A Methane Scenario

In reading recent posts about the methane “Arc tic time bomb” on the Neven Arctic blog (neven1.typepad.com), I realized that no one was developing a full-fledged scenario for how a serious methane emissions uptake from Arctic deposits could occur.  So here’s my (amateur) stab at it.

2007-2014

When, around 2007, the Northeast Passage opened up, few worried about the implications for methane emissions.  True, there were 50 Gt of methane locked up in methane clathrates (CH4 in a “water cage”), mostly under the shallow waters of the Arctic above Siberia, but it seemed there were several reasons not to worry:

• ·         Methane has a short half-life, unless it attains a concentration well above its concentration as of now;
• ·         It seemed then that even if the permafrost in which the clathrates resided melted, methane would only be released in a “bursty” manner by landslides caused by the loosening of the icy bonds of the underwater permafrosted land – certainly not in a steady stream such as would be needed to overcome the short half-life;
• ·         It also seemed that even if the methane was released from the clathrates, it would “pop” before reaching the surface, which in turn would mix more carbon with the water and hence put it in the atmosphere, or feed “blooms” which when they died each year would likewise release their carbon in the water and thence to the atmosphere – a fraction of the carbon already being emitted;
• ·         At present, the methane released (if any) was no more than a small fraction of the man-made amount of methane emissions – and that was still not near the danger point.

However, the warming water poured in from the North Atlantic along the western part of the Siberian Sea during the summer, and when Soviet researchers checked during the summer of 2012, methane bubbles hundreds of meters in diameter were coming up.  That meant that both the idea of “bursty” methane and the idea that all the methane would “pop” before reaching the surface were not accurate.  And yet, even during summer, the fluctuations detected amounted to less than 1% of methane emissions measured in the Arctic.  Clearly, some scientists argued, the other two factors (short half-life, small fraction of the total) meant that there was no immediate cause for concern.

And then el Nino arrived.

2015-2023

The splashier effects of el Nino distracted attention from its effects on methane emissions.  While it did indeed raise the temperatures down south significantly, its main effect was to warm the air in the Arctic (already in record-breaking territory) by 3 degrees in summer and by 10 degrees in winter.  The initial effect was to extend summer “insolation” (heating of ice and water from above) and above-freezing average air temperatures for 2 weeks on either end, so that the Arctic water was now just about completely ice-free and accumulating a “storage bank” of heat with which to melt the permafrost.

Now, the period of methane bubbles was lasting twice as long, and the pace of melting was four times as great.  Moreover, towards the end of the period, the small but steady warming of the Beafort Sea from the south was beginning to push into the eastern end of the seas above Siberia.  These, too, began to see bubbles and spikes in methane usage.

At the end of this period, another “distraction” arrived:  adjacent permafrost in Siberia began to thaw.  Although it was not clear in the beginning how much of that thaw would be methane and how much carbon, it turned out to be perhaps a 2/3-1/3 ratio.  Still, compared to human-caused methane emissions (which had gone up another 10% since 2007), the emissions from clathrates and the small contribution from Siberian permafrost were still much less.

2024-2032

Soon after 2025, la Nina arrived; but it had surprisingly little effect.  True, the ascent of temperatures in the Arctic slowed; but the warming water from previous years continued to pour into the Arctic.  That, in turn, extended the iceless Arctic period well into November, and the increasing energy in the air likewise extended the melting-out period over the Siberian seas into June.  And so, having quadrupled the last period, methane clathrate emissions tripled over this period, so that by 2033 worldwide methane emissions were up by 25% compared to 2007 – 15% from humans, 6% from methane clathrates, and 3% from land permafrost melt, which was undergoing its own steep climb.

Still, for a little while, the world could still file methane emissions in the Arctic under “lesser concerns”, at least compared to carbon emissions.  And there, as well, the contributions of carbon from permafrost were still minor compared to human emissions – not to mention the almost full effect of the decreased albedo of the Arctic.

2033-2040

These were the years when things got really serious.  El Nino returned, and the Arctic became ice-free year-round by around 2039.  The warm water year-round plus the increased insolation and the increased energy in the air year-round, transmitted to the water via storms, meant a quintupling of methane clathrate emissions – to a 30% increase over 2007.  Add on 10% from land permafrost and the 20% from human emissions, and methane emissions were up 60% -- an effect of much less than one degree F globally, but nonetheless significant.

And still the worst effects held off, until …

2041-2100

Methane clathrate emissions had reached somewhat of a “steady state”, in which melt reached progressively deeper into the permafrost, but the adjacent melted sediment continued to warm faster, as it penetrated to areas of greater pressure.  However, this “steady state” was adding about 50% more methane emissions than in 2007, at a steady pace.  Meanwhile, the permafrost contribution was steadily climbing, as melted permafrost converted to swamps which produced their own methane.  By about 2060, the result was a 100% increase in methane emissions in total – and that’s when the second shoe dropped.

Doubling methane emissions meant that the methane in the air was now saturated – it was far less likely to decompose into water and/or carbon dioxide.  As a result, the half-life of methane shot up, first to 20 years, and then to 40.  Now the other aspect of methane – that it is 70 times as powerful a greenhouse gas as carbon for the same half-life – began to come into play.  Effectively, the effect was 1 degree F of average global warming; but this was equivalent to the effect of the entire increase in carbon ppm in the atmosphere pre-2007.  To put it another way, methane added perhaps 33% to global warming up to 2070.

In the longer run, of course, carbon emissions continued to dominate for the next thousand years.  However, the land permafrost methane now assumed center stage, continuing the saturation for perhaps 300 of those years.  Global warming baked us; methane clathrates in the Arctic were the trigger to ensure that we were truly well done.

The Sad Implications of Two 2012 Climate Change Surprises

In reading postings in one of my favorite blogs recently (Neven’s superlative Arctic Sea Ice blog), it occurred to me that I hadn’t tried to summarize in my mind the two major surprises that scientists recognized in climate change last year.  What follows is my take on these surprises:

1.      Arctic methane is venting much faster than expected; and
2.        The weather effects of global warming are stronger than expected.

What are the implications?  Let’s take them one at a time.

Arctic Sea Ice and Methane

It still amazes me that most people did not see the likelihood that Arctic sea ice was going to take a nosedive to near zero in the 2013-2016 period, because I only had to apply some basic math when I first took a look in 2009:  exponential and normal curves.

Until recently, there was only one serious attempt to assess the volume of Arctic sea ice:  Maslowski’s PIOMAS model.  As I understand it, people tended to dismiss the model because Maslowski said:  this is the way I model Arctic sea ice dynamics, and therefore the sea ice volume should change over time in this and this way; and because he asserted without proof in his model that Arctic Ocean water temperature changes had a major role in increased melting over time.  However, when I saw that this model was constantly reality-tested by on-the-site sampling, even though each sample was of a small part of the overall Arctic Ocean, I realized that the long-term trends there were likely to be true.  And what Maslowski’s model showed, at any time of the year, was an exponentially decreasing Arctic sea ice volume.

By the way, recent Cryosat observations have definitively shown that, if anything, Maslowski’s model has underestimated the rate of volume decrease.

So why, I asked myself, do I not see corresponding decreases in Arctic sea ice area and extent?  As I looked at the dynamics of Arctic sea ice, I realized that that could only happen if there was a uniform distribution of Arctic sea ice thickness from, say, zero to twice the average thickness (at any time of year).  But what was really going on was that a certain percentage of the sea ice survived between years to become second year ice, third, and so on; but cue to currents, the average age of Arctic sea ice back in 1980 was five years – sooner or later, ice frozen at one end of the Arctic would reach the other end and head south into warmer waters, there to inevitably unfreeze.  Instead, thickness (with a little adjustment for the age of the ice) had much more of a normal distribution around the average. And that, in turn, meant that accelerated volume losses at, say, minimum would only show up in area and extent when we reached the fat part of the curve – which, it is now apparent, occurred in 2012.

By the way, the same logic also says that volume and the rest will not go to zero somewhere around 2014 – 2015; we will have reached the other thin end of the distribution, and the exponential decrease in volume will flatten out, exponentially.  That’s why I fully expect to see around 1-5% of the ice remaining at minimum until sometime around 2016-2020.

So, as I’ve said, I expected that Arctic sea ice would begin to obviously disappear around now, and I expected the climate change implications of this – including the fact that Russian-Arctic-Continental-shelf methane “clathrates” would begin to release their methane.  What I (and apparently others) did not expect was the scale of that release.  A Russian sampling of methane bubbling to the surface found huge pockets of the stuff – hundreds of times more than research had suggested might be the case.

Before I go on to discuss this, let me cycle back to the (expected) implications of Arctic sea ice melt.  Today’s models simply do not include melt to near zero at minimum in the 2013-16 time period, and a likely follow-on melt to near zero at all times of the year between 2035 and 2045. This in turn, will not directly lead to more carbon emissions.  What it will do is decrease Arctic Ocean albedo (from off-white-reflection to dark-blue-absorption of heat from the sun during the spring-summer-fall), and therefore warm up the Arctic Ocean portion of global and ocean temperature.  This already is 15-20 degrees Fahrenheit above normal during the summer; we are talking another 25-35 degrees by 2045, taking it to 20-25 degrees during the winter. 

The increased water and air temperature should therefore (a) accelerate methane clathrate melt, including that of the deeper waters nearer the North Pole, and (b) both cool and warm winter temperatures of more temperate zones – with the “warm” predominating over time.  How can (b) be?  Well, warmer Arctic air has more energy, and therefore pushes south against the “jet stream” more strongly, creating weather in which unusually cold Arctic air reaches further south periodically.  However, that same Arctic air is steadily warming over time, to the point where by 2050 it should be as warm as or warmer than southern winter air was in, say, 1980. 

Implications of the Methane Surprise

Part of the problem with assessing methane’s implications is that most if not all scientists have not factored in 2015-2045 Arctic sea ice melt’s implications for temperatures just a bit further south.  Because methane clathrate melt should be understood as part of a “double whammy” for methane – Arctic methane melt at the same time as permafrost melt.

Since (up to a point) methane has a very short half-life in the atmosphere (say, 8-10 years), you need a much greater rate of methane release into the atmosphere than carbon (all right, methane includes carbon too, but methane has a much greater effect on global warming per ppm than carbon dioxide) to achieve a comparable warming effect over time. And yet, studies of 55 million years ago, when the rate of warming was much less, indicates that methane had a major role in causing what Joe Romm at www.climateprogress.com calls “Hell and High Water”, with 90% of species wiped out.

Scientists have made a persuasive case for the idea that, even if methane clathrates are starting to melt and permafrost at the same time (i.e., even if we factor in Arctic sea ice melt), methane emissions will not reach a “danger point” where their effects in the atmosphere will rival that of carbon emissions any time soon – and therefore will avoid the main danger time of carbon emissions, before the lack of fossil-fuel reserves begins to decrease those emissions on its own). The problem is that the Russian observations indicate that those reassurances are based on assumptions about the rate of methane clathrate “bubble” occurrence that far underestimate their rate and/or amount.

So what, then, are the likely implications of this methane surprise?  As far as I can see, there are no “likely” implications, because the range of possible methane “bubble” rates, and therefore emission rates, over the next 40 years is so wide.   Nor is it clear to me, given that these emissions are occurring in such a localized northern area, just how wide an effect on global warming there will be.  However, my best guess is that over the next 40 years there will be a significant, localized effect:  Methane emissions will increase Russian and lower-Arctic-sea heat retention over what it would have been by perhaps 25%, with a corresponding increase in Arctic average temperature and Russian permafrost methane/carbon release.  This, in turn, may add perhaps ½ degree Celsius to global warming over the next 40 years – and, of course, will add a comparable amount over the 50 years following, at least – always remembering that a major fraction of methane released turns into carbon dioxide, and hangs around in the atmosphere for a hundred years or so on average.  In other words, the major effect of the surprise may be a more long-term one:  arrival of a ½ - 1 degree Celsius additional increase in “thousand-year” global warming now rather than later, when it would have less practical effect.   

The Weather Effect Surprise and Implications

Taking my cue from James Hansen and Joe Romm, I had guesstimated in 2009 that we in the US would first see constant, undeniable reminders that global warming is real in the 2020-2025 timeframe.  These reminders would include not only “hundred-year” hurricane-type wind speeds and scorching summers that created Dust-Bowl conditions in many areas, but also an overall burden of disasters that reached 0.1% of GDP even for a country like the US.  I believe it was Heidi Cullen that imagined NYC missing a massive hurricane in 2017 and getting one in 2041, by which time the city was prepared and the sewers did not back up and overflow, causing hundreds of thousands of deaths from disease.

But, as Joe Romm noted in his blog, the things that should have been expected in 2020-2025 seem to be happening in 2011-2012, ranging from devastating Australian rainstorms to stupendous Russian wildfires to Hurricane Sandy and its 13-foot storm surge (still short of the 20-odd-foot storm surge that might cause the sewer outlets to be closed and the sewers to back up, but enough to flood the subways and make downtown Manhattan, Queens, and Staten Island disaster areas).  It appears that the monetary effects of disasters globally, according to insurers like Munich Re, are 10 times what they were a decade ago, and there is no reason why they should not continue to double or triple by 10 years from now – meaning that the timetable for effects on global GDP should perhaps be moved up by 3-5 years.

The surprise is not that global warming is happening faster than predicted – globally, 2012 was actually about average for the last decade, which in turn means that it was one of the “dips” in our steady, accelerating global temperature ascent. The surprise is that the effects on weather were larger than expected.  What I suspect is that forecasts simply assumed that certain catastrophic events would happen more frequently than expected, but could not predict that these catastrophes would spread to areas where they had not before (devastating tornadoes in western Massachusetts), areas that were less adapted to a new set of weather patterns. We are reaching the point where we have not only extremes of existing weather patterns, but also new climates that produce new weather patterns.

And so, I also suspect that the effects of the “weather is changing faster than we expect” surprise are, like the methane surprise, bad but unpredictable.  I anticipate that the Nino/Nina cycle and North Atlantic Oscillation patterns that have driven weather around here since time immemorial (i.e., the last 5,000 years) are changing, but will manifest first in longer versions of the extremes of this cycle – and that’s a total guess.  Certainly, an extended Nino would mean even greater Dust Bowl conditions and summer heat over a great extent of the US for longer than ever before, even leaving out the effects of the ongoing global temperature warming.  Initial predictions show the US except the Northeast and Pennsylvania in catastrophic drought conditions in 2050 – is it possible it could happen before then?

Boy, I hope not. But, as a clueless Presidential candidate noted in 2008, hope is not a plan.

Conclusions

Overall, oddly enough, the implications of these surprises for me are not great.  I concluded in 2009 that we desperately needed to cut carbon emissions in absolute terms by 40% 2010-2020, and another 40% 2020-2030.  Since then, with extremely minor exceptions, all major countries in the world have utterly wasted their time in that regard.  In fact, my definition of functional insanity is to see oil companies and countries seeing Arctic sea ice melt as an opportunity for increased drilling of fossil-fuel carbon pollutants, and the United States seeing a Keystone XL pipeline that solidifies tar-sand drilling that sharply increases the likelihood of the end of all life on Earth as an opportunity worth considering, much less actually being relatively close to implementing it.

So, to my eyes, the horrible effects of the two 2012 surprises simply speed up what’s coming and increase its bad effects in relatively minor ways, and that will be worth it if people wake up now and start doing something globally effective.  Except that there’s little sign as yet that people and their leaders are even beginning to understand the urgency of an adequate scale of action.

I wonder what new surprises 2013 will bring?  I could really use some good news.

In Praise of neven1.typepad.com

Somewhere around two years ago, iirc, I happened on this blog. I had, as I remember, found it indirectly. I had been following Paul Krugman the economist for about 25 years, and saw in his NY Times blog a reference to Joe Romm’s blog on climate change.  Since I had recently been made aware by some public library books like A World Without Ice and Storms of My Grandchildren (Hansen), not to mention a summary of the IPCC 2007 report, of the importance of the subject, I followed Prof. Krugman’s pointer to www.climateprogress.com. There I happily followed Mr. Romm’s pointers to in-depth recent research and other ways to sharpen my understanding of the subject.  And then he pointed me to a blog on Arctic Sea Ice – neven1.typepad.com.

It has been an extraordinary two years of reading, and a very rewarding journey. I must therefore give full credit up front to its presiding spirit, Neven – of whom I confess I know very little, aside from the facts that he is Dutch and that he apparently at one point considered trying to find a retirement place in Tasmania.

What has made my time following this blog so very rewarding, aside from the importance and urgency of the subject matter – about which I have written many times before, and will, I’m sure, again – is the sheer richness and variety of the accessible information available to the patient lurker. This was not fully apparent at the start. Indeed, my memory of my first impressions was that this was a site trying to piggyback off not very available scientific data on trends in Arctic sea ice, and having to fend off “climate denialists” attempted to clutter up the comments at the same time.

“Denialists” were, of course, yet another variant on the garden-variety “troll” that I had first seen in 1981 with my first experience of the Internet and newsgroups. As had been increasingly happening since the late 1990s, they made up in pack mentality and corporate encouragement for their decreasing skills in swearing and logic. Nevertheless, they posed a danger to all decent blogs:  that the “moderator”/blog poster would become so taken up with warring with denialists that their great value in conveying new information outside the traditional structures of academia and the like would be completely diluted – something that concerns me about Climate Central to this day.

However, over the last two years, I find that I have gotten as much if not more solid scientific background from neven1.typepad.com on certain subjects than even www.climateprogress.com.  Consider the following:

• ·         The early/final stages of sea ice freezing/melt, which can deceive instruments and therefore forecasts, but which we have learned to adjust for – melt ponds and the like.
• ·         The strange case in which global warming can decrease Antarctic land ice and yet initially increase Antarctic sea ice (by about 1% per decade).
• ·         The role of wind and current in propelling any individual chunk of Arctic sea ice across the top of the world, to eventually melt in the northern Atlantic.
• ·         The role of insolation and changed albedo, not just in speeding existing ice melt but also in having follow-on effects on world climate.
• ·         The effect of Arctic sea ice melt on Greenland land ice melt rates, not to mention the speedup in both from added global warming in the summer in the north.
• ·         The effects of warmer water currents as opposed to warmer air temperatures in speeding melt.
• ·         The alarming role of methane, of which Arctic may be as much as a sixth of the sources of this greenhouse gas in the next century.

All this plus the mixed joy of watching a terrible but fascinating race, in which I at the same time guess a certain minimum area, extent, and volume of Arctic sea ice for a year, and “root” for the correctness of my guess, and still dread the possibility that I will continue to be more or less right – which would mean that most even of the concerned and reasonable are underestimating the speed with which disaster is approaching.  After all, we still hear forecasts of 2100 for less than 5% Arctic sea ice cover at minimum, or 2045, or 2030, but the Maslowski projection of 2013-2016 (which I think translates to 2016-2020) is still rarely espoused – and that’s what I predict and fear.

Back in 2010, as I recall, everyone was hung up on extent statistics, because area was less volatile and volume measurements were distrusted (wrongly, I believe). And so, we got our daily fix by betting on extent minima and neven1.typepad.com pretty much closed up during the winter, with cute pictures of polar bears and other hibernating creatures. Today, there is an extraordinary wealth of graphs to look at, about extent, area, volume, thickness, and their trends, as well as the climate equivalent of “radar”: pictures of daily ice concentrations. I don’t know what this winter will bring, but last winter was quite busy, what with methane, discussions of trends in sea ice maxima, and discussions of shifts in weather patterns in North America and North Eurasia due to changes in the North Atlantic dipole anomaly. Somehow, I think the blog will find it hard to hibernate this year as well.

Because it is apparent even now, more than a month from any minima, that this year is a continuation of the trend, and it is going to be bad. There’s perhaps a 5% chance that there won’t be a new area minimum, to accompany yet another new volume minimum and a likely possible extent minimum. The “radar”, for the first time, is showing bits and pieces of ice rather than dense concentrations, closer and closer to the Pole, and the thickness projections for 5 days from now are for very thin ice within 3 degrees of the Pole. So now, the question will be, how long into October will the Arctic waters hold the warmth of the summer sun beating down on open water until sometime in September? As we enter a new normal of longer and longer periods of ice-free Arctic waters, how long will the gloom of night and lower temperatures in Arctic winter stave off the prospect of an ice-free Arctic year-round, not only increasing global temperatures from lower albedo but also possibly unlocking more stores of methane?

And the last month has seen an extraordinary series of blog posts by Neven and comments by perennial commenters to enhance the understanding and richness of Arctic (and Greenland) ice analysis – to the point where Neven is almost becoming a fixture on www.climateprogress.com.

And so, I recommend to the two or three people who actually read this blog the guilty pleasure (?) of reading neven1.typepad.com for your daily fix of extent and area figures, and for the extraordinary bursts of mixed opinion and analysis that follow. As with every blog, in the comments there are gems and there is manure; but the proportion of gems lately is quite high, imho. And no, I haven’t said anything for weeks; what need?

I reluctantly followed a link to Anthony Watts’ denialist site today, and was struck by an amazing realization:  it wasn’t just that they were living in another world, it was a much poorer world.  There was no discussion of melt ponds, or possible cyclones that might break up the ice and melt it further; in fact, there was nothing, except general discussion by people obviously not that interested in learning more about just how things worked.  To misquote George Bernard Shaw in Man and Superman, it wasn’t  just that they were wrong, it was that they were extraordinarily uninteresting.

And then there’s neven1.typepad.com. Here’s to another two wonderful and terrible years. And thanks. Thanks for so much.

Methane Update: Less Worried, Still Very Worried

I just saw an interview by Skeptical Science with Ms. Sharapova, a Russian scientist, on the Russian findings that sparked my recent methane worries. Her responses clarified the answers to the main questions I had about Arctic sea methane clathrates. Her key information, imho, was the following:

1. The Russians recently discovered that methane clathrates could form not just in the 200-1000 m depth range, but also in the 20-200 m range.
2. They also found that clathrates there did not just melt from the top down; they also melted in pockets below the surface melt.
3. The 2011 survey, for the first time, looked at the 20-200 m Siberian coastal shelf, rather than the 200-2000 m deeper waters.

Let’s look at the implications for my methane analysis. In the first place, this explains why methane was able to bubble to the surface, instead of popping or being eaten by methane-munching bacteria: it was too close to the surface, and especially if, as appears to have been the case, it was being released in larger chunks/bubbles.

In the second place, this appears to indicate that the ramp-up in methane emissions at any particular point is less than I feared. There are several possible reasons to anticipate that at greater depths, methane release from the sediment would ramp up more slowly than a 100-fold increase in one year. Likewise, there are several possible reasons to anticipate that initial methane releases from the shallow continental shelves would be greater than that from deeper areas, if there were methane clathrates there in the first place.

However, in the third place, this newly discovered source of methane clathrates appears to be a much bigger source of emissions, both in terms of melting more rapidly and of having more methane stored to begin with. Because sea shelves slope more rapidly the deeper they get (to a point beyond 1000 m), the sea-surface area of 20-200 m deep shelves is comparable to the sea-surface area of 200-1000 m ones.

Under the surface, the methane clathrates can be stored much deeper before earth heating and pressure melt them. Take these two things together, and the amount of methane in Arctic clathrates may be 2-4 times the amount previously estimated. Meanwhile, this 20-200 m range lies almost entirely in the “shallow ocean” range where warming currents from the south plus warming of newly exposed surface waters by the summer sun create hotter water next to the sediment – and thus melt things faster. These points are confirmed by the observations of rapid bubble generation and much larger funnels from which methane flows in the 20-200 m range.

In the fourth place, the ability of 20-200 m methane bubbles to rise to the surface means that we probably grossly underestimate the percentage of emitted methane that will rise into the atmosphere as methane rather than carbon dioxide. Frankly, this is probably good news, since that means less of it will eventually stay in the atmosphere as carbon dioxide – but there’s still a chance it may stay as methane for a long time – and be far worse for global warming. This would happen if there’s too much methane up there and the OH in the atmosphere that removes a lot of that methane runs out, a possibility some scientists have raised.

In the fifth place, the existence of pockets indicates that methane emissions may be bursty, as surface melt “burns through” to those pockets that are themselves melted, but are still trapped by frozen clathrates above. Those bursts should be frequent enough to keep methane emissions at a higher yearly rate.

Implications

Overall, this makes me a little more hopeful about overall methane emissions and their effect on global warming. While there is perhaps 2-4 times the amount of methane clathrates to emit than I thought, there may be 30-70% lower emission rates than I anticipated, and that’s the key to methane’s overall effect in the next 160 years, when it matters. To put it another way, the net methane emission rates per year should be lower than I expected, and the amount in the atmosphere as methane in the next 160 years should be lower than my worst-case all-methane scenario (assuming there’s enough OH). Hopefully, the amount of carbon dioxide should be lower as well, because of the decreased yearly emissions amount and increased percentage arriving as methane (only half of that turns into carbon dioxide). However, this isn’t sure, because if the OH runs out, the effect of yet more “steady state” methane over, say, 600 years on global warming will be worse than I had anticipated.

All in all, I would now tend to put the likely overall new natural-source methane emission effects (also including permafrost and wetlands) in the 3-6 degree C range over the next over the next 200 years, and in the 2-5 degree Celsius range in the 400 years after that – overall, perhaps a 25% boost to global warming rather than a 50% one, protracted over more years. High water may not be delayed, but hell may be a little less hellish in temperature, and the end of life on earth ever so slightly less likely, than I feared.

Unless, of course, the OH in the atmosphere runs out … the worries never end, do they?

Methane Talk-Down: Partial

One of the true joys of learning about science – as opposed to, say, economics – is that eventually you can usually get to a scientific summary that clears up many of the distortions that popular reports create. In the midst of wading through yet another cherry-picked-evidence blog post (this one on methane) by Andrew Revkin of the NY Times, it suddenly occurred to me that I should check out Justin Gillis of the Times, whose posts have been praised iirc by Joe Romm of climateprogress fame. Gillis’ reporting still seemed a little superficial to me, but he had a link to a 2006 scientific summary of the research about methane and climate change, an oldie but goodie where I found the answers to many of my questions. My recent blog post on methane laid out the doomsday scenario that I fear; Chapter 6 of this summary, as Rachel Maddow would say, talked me down – but only partially.

Because the broad scenario that I laid out is not drastically affected by the information in the summary, it is easier to lay out the summary’s picture of methane and then, at the end, note how this may affect my scenario. I will focus on methane clathrates, since the changes to everything else are less substantial. And, of course, I am sure that more misconceptions remain – because a summary article of ongoing research can’t be expected to answer everything. Anyway, let’s begin.

Methane Clathrates, Water Methane

Last time, I presented a very summarized picture of natural-source methane as coming from three sources: methane clathrates under the sea, permafrost on land at high latitudes, and peat bogs next to the permafrost or in the tropics. It turns out that the picture is a bit more complicated, and the complications matter.

To start with, methane clathrates are formed and remain stable in sea-floor sediment in particular combinations of sea temperature and pressure from the sea above that limit them to the sea floor somewhere between 200 meters and 1000 meters below sea level. In other words, the water has to be near zero F, and the clathrate has to be lower than 200 meters below sea level and higher than 1000 meters below sea level. Between those two limits, the deeper the sea floor, the wider the zone in the sediment where it can exist. Guesstimates for a typical clathrate “stability zone depth” might be 250-300 meters. Btw, a confusing part of the scientific lingo apparently refers to Arctic clathrates as “subsea permafrost.”

What happens to melt the clathrates? The water next to the sea floor warms up, or warmer temps further up the sea slope cause the equivalent of a mudslide on the sea floor that basically slices through the clathrate, stirs up everything above the slice as a cloud of sediment, and melts all the clathrate above the new sea floor. That is what they think happened at Storegg, a place near Norway where there is a “crater” 30 km across that may have released a gigaton of carbon, all at once (methane is CH4).

Now here’s an odd part. We are used to thinking of gas coming up to the surface in bubbles and releasing itself into the atmosphere when the bubble pops. Not so with clathrate methane – most bubbles pop long before they rise the 200 meters or more to the surface, according to the models. Instead, one of several things happens: the methane rises to the surface but not as bubbles (it is “buoyant”) and then releases into the atmosphere, or it is eaten by methane-eating bacteria, or it converts (typically to carbon dioxide) en route. Initial indications are that a small percentage of melted clathrate should rise to the surface combined with water and is released into the atmosphere as methane, which happens effectively immediately; a large percentage should be eaten by bacteria, who convert it into carbon dioxide on the surface of the sea, and the carbon dioxide is released into the atmosphere in order to equalize atmospheric and oceanic CO2; and a medium-sized percentage should convert to carbon dioxide without going through the bacteria, to be released into the atmosphere as carbon dioxide in the same way.

The methane clathrates in the Arctic seas contain perhaps 50%-80% of all clathrates. They are also by far the most likely to be affected by global warming, since water temperature variation due to increased sunlight on the water and increased temps of sun-warmed currents from the south are widest there.

Other Methane Sources

The picture of land-based methane sources also needs amendment. It appears that much of the methane stored in permafrost is stored in peat within the permafrost – which can extend as far down as 200 meters or so. Meanwhile, wetlands at whatever latitude are generators of methane, the Amazon as much as Ireland. When the permafrost melts, the water plus peat turns into a bog that (under global warming) is maintained by increased precipitation: that’s what often drives increased methane production.

Here, the translation to the atmosphere is more clear. Melting of permafrost releases any methane locked in the ice (but not in clathrates), and also creates new constantly-emitting sources of methane. Likewise, wetlands inject methane directly into the atmosphere.

Now we come to the tricky part. We are accustomed to thinking of methane in the atmosphere as separate from carbon dioxide. Not so. What often happens to methane in the atmosphere is that it "oxidizes”, which typically means that one of the hydrogen atoms is broken off to help form H2O (water), while the rest forms a methyl group (CH3) which eventually breaks down to carbon dioxide. In other words, much of the methane tossed into the atmosphere actually winds up as the major greenhouse gas, and stays up there for 150-250 years.

What’s the Effect? Um …

OK, so now the scientist wants to figure out what the global-warming effect of unlocking all that methane is going to be. The problem is that we have two sources of comparison, and neither of them is great.

The first is to use what happens over 10-20,000 years immediately after a Milankovitch-cycle minimum (a “glaciation”) as a model. Using that model, scientists have pretty well determined that in such times of rising global temperatures, the amount of methane in the atmosphere probably doesn’t vary by a heck of a lot, and the effects on global temps compared to atmospheric carbon are pretty minimal. Methane melt in general might have a role in things like sea-ice melting near Greenland, which has been shown to have surprisingly wide effects on global climate, but most of the good candidates for that type of melt (subsea, permafrost, wetlands) just don’t make a strong case for themselves.

The problem with this type of analysis is that it looks only at periods when most of the ice remains – because that’s what happens at the peak temps of a Milankovitch cycle. We have almost certainly moved above those peak temps in the last couple of decades, and so we are in much less charted waters. For a period much more comparable, you have to go back to the PETM – 55 million years ago.

OK, in the PETM, temps were 5-10 degrees C warmer than now. Increases in carbon in the atmosphere just don’t seem to be enough to justify those warmer temps. So for a while, there were theories floating around that methane was the complete reason for that kind of warming – no carbon needed. That would have been nice, since figuring out why carbon suddenly spiked in the first place, not to mention why the time period of this rapid warming was around 20,000 years as the latest research suggests, has been a headache. Bad news: there simply doesn’t seem to be a natural source of methane that comes near to explaining the whole temperature rise, not to mention keeping going for 20,000 years. So it looks like we have a choice between carbon emissions plus “unknown”, and carbon plus methane. Tentatively, the scientists are voting for carbon plus methane.

But the PETM isn’t great as a model, either. The problem there is that things happened slowly compared to today. If we say that the carbon atmospheric-concentration rise then happened over the course of 20,000 years, well, our carbon rise appears to be happening over 350 years – and it may very well double the rise of the PETM over the course of those 350 years. In other words, this is happening at least a hundred times faster. And, as we’ve seen in the case of carbon, that can mean that the positive follow-on effects happen well before the negative “stabilizer” effects. So, for example, don’t necessarily expect the magical munching methane sea bacteria to appear in the Arctic and save the day.

OK, so the models we have aren’t great. Can we at least use them for some guesstimates?

Preliminary Guesses

Well, the scientists have done the guessing for me. The key sentences I find in Chapter 6 say, more or less (with the usual caveats about my understanding), that the amount of atmospheric methane from natural sources pre-Industrial Revolution equals the amount of methane added from human sources since then, which equals the likely amount of methane to be added at some point due to all natural sources except subsea methane, which equals the potential amount of methane from subsea methane. In other words, in a worst-case scenario with 2006 models, at some point in the next 300 years, we might expect atmospheric methane four times what it was in 1850.

How much added heating would that translate to? Again, reading between the lines, perhaps 1 degree C from the methane alone. However, if we take the PETM as a model, it might be more like 2 degrees C. And that’s the maximum, so we can all semi-relax, right?

Well, no. You see, there are two problems. First of all there’s the fact that much of that methane is going to convert to carbon dioxide when it’s up there. Second, there’s the fact that the more methane gets into the atmosphere from now on, the longer it sits there. The 2006 estimate was that methane hangs up in the atmosphere an average of 9 years. But at twice the concentration, I think we can count on it sitting up there for 12-18 years on average. So those two things should add another ½-1 degrees C to the “additive effect” of methane in the atmosphere.

And then, of course, there’s the question of methane that converts to carbon dioxide before it gets into the atmosphere. Here, the summary didn’t really have much to add in the long term. Even by their time-frame estimates, all that methane-to-carbon-dioxide, even if it doesn’t get there in the next 100 years, will almost certainly show up in the next 1000 years. So it’s a more extreme version of my “pay me now or pay me later” scenario – except that we can at least hope that by the time the methane-turned-carbon-dioxide shows up, we will have managed to cut down on our human-caused carbon emissions and the amount in the atmosphere will have begun to go downhill significantly.

All in all, not great, but not as bad as my full doomsday scenario. Instead of 6 degrees C from methane-turned-CO2, perhaps 2-3, although that increase will stick around for maybe twice as long; instead of 7-9 degrees C from methane-stayed-methane over the next 160 years, perhaps 1-2 degrees over the next 300-500 years. And it will happen more gradually, so it won’t be really noticeable, probably, for the next 30-40 years. Except …

I’m Not All the Way Down

Read carefully the interview with the head of the survey of methane releases in the Siberian Sea. He states, effectively, that the diameter of the “craters” I referred to earlier had increased by up to 100 times this year, and this methane was “bubbling to the surface.” If you look at the 2006 summary, neither is supposed to happen. Very little methane should arise to the surface in a bubble, as noted above, and the methane hydrates should not suddenly do a big jump in melting: and 5 degrees C increase in water temps (since 1984, a jump of 2.1 degrees C has been observed) should cause perhaps 1 meter’s worth or less of methane hydrates to melt over the next 40-80 years – and it can’t be explained as mudslides, since it has happened in quite a few places.

So why would scientists’ models be wrong? Well, in the first place, they assume that relative sea-water warming will only occur in a short space in the summer, when the ice is melted and the sun warms its top. However, the depth of the surface ice in winter is also less than before, and the water carried by currents from the south is warmer. Clearly, it’s very possible that scientists are underestimating the amount of melting going on the rest of the year. Add this to the known problems with the original model developed in 1995, and you have some, but maybe not all, of the increase in clathrate atmospheric methane release explained.

The second flaw may be the modeled prediction that very little methane melt will rise to the surface as bubbles. Why might this model be wrong? I don’t have a clear answer from the summary – it could be that the turbulence of the water keeps the bubble from popping, although that seems unlikely. One thing seems clear: the magical munching methane bacteria are nowhere to be seen.

And the third flaw, which also affects the land methane emissions rate, is a major underestimate in the models of the rate of global warming. The models implicitly assume that the Arctic sea ice won’t melt entirely in summer before somewhere between 2030 and 2100, and year-round perhaps never – that one seems clearly wrong. Therefore, they underestimate the speed of the follow-on effects, including much faster warming of water within 100 meters of the surface, which would inevitably mean much faster warming at the 200-500 meter level – sorry, that’s not “deep ocean.”

In other words, what the latest information is telling us is that the semi-comforting story I just gave you is almost certainly an underestimate. The “true” effect of methane is somewhere between my doomsday estimate and the one above – except that the roles of methane-stayed-methane and methane-turned-carbon-dioxide have switched, because we now know that much of that atmospheric methane is going to change to carbon dioxide while it’s up there.

I find the logic of the summary convincing as well as semi-comforting; so if I had to guess, I would say that the net effect is somewhere between 3-5 degrees C, mainly in carbon dioxide, and spiking over the next 40-150 years before leveling off. But that’s a complete guess. Until I understand just how the models went wrong, I’m only partially talked down from my panic. So here’s to the New Year: It will be a season of hope, it will be a season of despair, it will be a season of enormous impatience until the first scientific explanations come out.

Methane: The Final Shoe

Recently, Neven’s blog on Arctic sea ice (neven1.typepad.com) featured a new post on recent scientific observations of methane – observations that Neven said made him “sick to my stomach.” I am not as easily panicked – I reserved my stomach sickness for a recent British report about how most life in the oceans, except jellyfish, will be dead within the century unless we do far more than we are doing. However, I do understand his reaction. Effectively, these reports indicate that the dreaded “final shoe” of global warming, the one reinforcing side-effect of global warming that we hoped against hope would not happen, appears to be partially beginning to drop. Moreover, it seems clear to me that most if not all folks, even those who are aware of methane’s role in climate, are underestimating its potential impact in causing additional and more rapid murder, disaster, and then catastrophe.

So here is my understanding of methane’s role in our tragedy – for yes, some small tragedy is unavoidable now, even without methane’s impact and even if we do everything we can from now on. I am sure that as an amateur I am missing or misrepresenting some points. I am also pretty sure that most amateur commentators are doing far worse. If I were you, I would not take comfort from any of this post’s stumbles or missteps.

How It Works

Methane is CH4, or a carbon atom with four hydrogen atoms. It is, imho, the second most important “greenhouse gas”, and to understand its effects it is best to compare it with carbon tossed into the atmosphere and combined with oxygen to form CO2, or carbon dioxide.

Here’s how carbon emissions that form carbon dioxide work (excess detail stripped away). As they ascend in the air they combine with the oxygen to form carbon dioxide. Most of that carbon dioxide sits in the atmosphere for perhaps 150 years, and most of the carbon has fallen to earth again within 250 years. While it is up there, doubling the amount of carbon (in CO2 form) in the atmosphere adds about 3 degrees C to global temperatures, and double that in the far north and south, especially in the winter. The “normal” rate of carbon in the atmosphere is 250-280 ppm (parts per million), and we are presently somewhere around 395 ppm.

Methane emissions work in a similar fashion, but with some important differences. In the first place, methane is typically stored in the earth and emitted as a gas – i.e., not as carbon but as CH4. Once it gets into the air, it can either split the carbon atom to form carbon dioxide – hence increasing that greenhouse gas – or remain as methane. If it stays methane, most of it stays in the atmosphere for 10 years, and most is gone after 15 years. So what’s the problem?

Well, the problem is that while methane is in the atmosphere it has up to 70 times the impact on global warming of comparable amounts of carbon dioxide. I find it useful here to imagine the old image of keeping a ping-pong ball in the air with jets blowing from beneath. If I toss a ball of carbon dioxide in the air, it stays up there for 200 years. With methane, I have to keep blowing like crazy – or, if you like, adding the same number of new balls of methane every 12 years. But if I keep an amount of methane in the atmosphere comparable to doubling carbon dioxide, then I drive up temps not by 3 degrees C, but by 100 degrees C. No, we haven’t gotten to the worrisome part yet.

In other words, the effects of increased amounts of atmospheric methane, piled on top of increasing carbon dioxide from other sources, fall somewhere in between two extremes. At one extreme, all the methane turns into carbon dioxide, and hangs there for 150-250 years. As we will see, that means that carbon dioxide may double or quadruple compared to global warming without intervention by methane, for an additional 3-6 degree C global warming. At the other extreme, all the methane stays methane. As we will see, a reasonable guess for its effects then is a 12-18 degree C additional increase starting somewhere around 20 years from now and going for 120 years, and then fading out. To put it bluntly: we roast more now (stays methane) or we fry more later (changes to carbon dioxide).

The Real Worry

So where are these new methane emissions coming from? Mainly, there are two potential types of source. The first is human-caused activity: just as we emit more carbon by burning fossil fuels as our population and industry grows, so emissions of methane for industry and personal tasks and by increasing populations of farm animals like cows increases accordingly. The second is methane frozen in the earth between periods of unusual global warming. That methane lies in three main places:

i. The shallow Arctic seas, especially the shallow Siberian sea north of Russia, where it is frozen not in ice but in a comparable substance known as a clathrate;

ii. The permafrost of Siberia and northern Canada/Alaska, where it is locked in frozen ground tens of meters deep on top of unfrozen earth;

iii. The peat bogs further south, where it is often mixed with water.

The methane emissions from our first type of source have caused methane in the atmosphere to shoot up fairly steadily over the last 100-odd years, so that methane is now a significant contributor to today’s global warming. It would be a really excellent idea to cut down on it. However, to some extent that increase has apparently leveled off. No, what really scares us over the next 200 years is the second set of sources.

The last time the globe apparently became (not when it was, when it became) this warm or warmer – maybe 55 million years ago, in what is called the Paleocene-Eocene Thermal Maximum, or PETM for short – it seems very likely that methane from the second source type was indeed emitted in quantity as methane, as that is a very good explanation for why temps actually went a little higher than the amount of carbon dioxide in the air would seem to dictate. However, that should not give us comfort. Ken Caldeira in Nature notes that methane of this type was stored in much smaller quantities then. That would mean that methane from sources i-iii emitted now would either (a) have similar effects over a much longer period of time or (b) would have much greater effects over the same period of time. So which is it, (a) or (b)?

Well, one obvious factor in deciding between (a) and (b) is how fast our global temps are going up already, before we start emitting i-iii. Once we start that faster rate of emissions, of course, that will speed up global warming even further, so we can bet that a faster initial rate of global-temp increase will keep methane emissions higher right throughout the process. And every available bit of evidence points to the fact that we are warming already much faster than in the PETM – because we humans are emitting carbon stored in the earth as “fossil fuels” (really, mostly decayed vegetable matter) much faster.

All right, so it’s faster. Is it fast enough to worry about? Here we have to consider sources i, ii, and iii separately. Methane clathrates are apparently a big honking source of methane, according to scientific estimates. No one is entirely sure about how fast these clathrates will “melt” and methane bubbles will rise to the surface, once they start melting. However, they are sitting in shallow seas and they start right at the surface of the sea-floor. We know what it takes: warming of the water above the clathrates. And that has been happening, as the Arctic sea ice in that area at the top of the water melts in the summer where it hasn’t before, the sun beats down on the newly-exposed water to heat it, and warmer water from the south moves in.

Now let’s consider ii. Joe Romm at www.thinkprogress.com has an extended post focusing on this source. The net of what he has to say is: Methane stored in permafrost is comparable in amount to methane stored in clathrates – big and honking. Permafrost melting is already underway at a brisk pace. Projections that are unrealistically conservative about how fast global warming will occur project that methane/carbon dioxide emissions from that permafrost will reach a high level about 20 years from now and continue at that level or somewhat higher for 120 years, at which point most of the permafrost will be gone. Make your own adjustments – however you adjust, it’s going to reach a higher level than that sooner, and stay there for a shorter period of time. Is that enough, by itself, to worry about? You betcha.

Then there’s iii – peat bogs and wetlands, even in the tropics. It’s not clear that there is as much methane there, or that it will be released as quickly. Remember, the further south (north, for the Southern Hemisphere) you go, the slower the rate of global warming. But it’s very clear that it’s happening. That was what the Russian summer fires were all about: global warming led to warmer temperatures that dried up the peat bogs and they went up in smoke, releasing methane. My totally random guesstimate is that peat bog methane emissions will follow much the same trajectory as those in i and ii, and will therefore have ½ to ¼ the impact at any one time or overall of either i or ii.

Now let’s reach ahead and note that things get drastically worse if all of these emissions increases happen over the same period of time – somewhere around 2-2.5 times worse. Luckily, so far emissions source i has not yet kicked in. Scientists report that as of 2010, there were no atmospheric signs of unusual methane or CO2 from Arctic sea sources. Be careful. There’s a trick in that statement.

Doing the Math

Before we hurry on to our conclusion, let’s pause and see if we can nail down a little better what those effects are likely to be if all three sources of the second type fire off fast at the same time. In particular, let’s assume a scenario like that predicted for source ii, only this time with all three sources emitting like crazy.

One estimate has the amount of stored methane, converted to carbon dioxide, at about 7 times the amount in the atmosphere right now. Let’s assume that, starting 20 years from now, this emits about 1/3 of itself at a fairly steady rate over the course of the following 160 years. So, 2.3 times 400 ppm or 920 ppm is the amount added to the atmosphere by 2170, on top of the existing amount (400 ppm) and the amount estimated to be added to the atmosphere by 2100 under “business as usual” (900 ppm). We’re up to about 7-9 degrees C global warming somewhere between 2100 and 2150. Even if we cut our emissions to zero today (totally unrealistic), we’re up to 5-7 degrees Celsius.

If you want to be gloomy, you can assume almost all the methane, turned to carbon dioxide, vents in the same time period. Add on another 1800 ppm, and then add on another 500 ppm for continuing “business as usual” between 2100 and 2170. Now we’re talking 12 degrees C.

OK, same thing, but it all stays methane. If you remember, this is over 160 years, but methane falls from the sky after about 12 years, so we’re talking about 12/160 = 1/12.33 of the equivalent amount of carbon dioxide on an ongoing basis over that 160 years. However, that methane has perhaps 33 times the effect on temps while it’s up there. So starting 20 years from now, there is an overall jump of about 8 degrees C on top of the effect from carbon dioxide noted above – and that effect lasts for 160-odd years. That baked-in non-methane carbon dioxide effect is going to be around 3 degrees C under the most optimistic of assumptions, and could go as high as 9 degrees C. And remember, if you want to be gloomy, tack on an additional 6 degrees C from emitting almost all the methane.

So here’s your two extremes. If you’re lucky, it’ll all go up as methane, and fall right down again. Now we’re talking 11-23 degrees C global warming between 2030 and 2190, and we fall down to a nice comfortable 6 degrees C after that. If you’re unlucky, it’ll all go up as carbon dioxide, in which case we’ll see maybe 8 degrees C of global warming from 2050 to about 2330. By the way, initial estimates are that more of it will rise as carbon dioxide.

The best part of this analysis is that I left out other “positive forcings.” In particular, I left out the fact that all this warming is going to turn part of the ocean (The Arctic and Antarctic) and part of the land (all those nasty glaciers) darker, from white (snow) and off-white (ice) to dark brown and green (land) and dark blue (ocean). Darker colors store heat. I’m not sure what how much warming effect that will have, but scientific estimates suggest indirectly (it’s included in some scientific estimates suggesting 3-6 degrees additional warming beyond that due to carbon dioxide in the atmosphere) that it’s likely to be at least an additional 1 degree C. Icing on the cake. Or not icing.

The Best Part

Now back to that trick. You noticed, didn’t you, that I said “as of 2010.” Well, the recent article cited by Neven said that a Russian scientist reported that in their annual sample of Siberian Sea methane emissions, which they had been doing for 20 years, for the first time ever they were seeing, not “funnels” of tens of meters across from which methane was bubbling up, but lots of funnels “more than a thousand meters across”. Do the math: that’s between 1000 and 10,000 times the rate they had ever seen before. He was very confident that results across much of the Siberian Sea would be similar. Is that enough to signal the start of Arctic sea methane emissions on the scale we’ve been talking about? How can it not be enough?

Now let’s add the usual caveats: wide variance inherent in the estimates, lack of confirming evidence in some areas, uncertainties in data collection, blah, blah. The scientist’s reaction to these is to minimize the impact by stating the most likely impact of which he or she can be certain. The realistic reaction is to ask what is the impact of median likelihood, with equal likelihood of a lesser or greater impact – and, as far as I can tell, that’s what I’ve given you.

And, by the way, don’t bother to object that present projections don’t show this. Guess what – most models don’t consider the impact of even one natural methane source behaving this way, and the rest (only recently) of just one (permafrost).
Like I said, I don’t get sick to my stomach about this – because I did my own guesstimates more than a year ago and got my puking done then. I’m still hoping that the methane shoe will drop more slowly; and also that I’ll win the lottery. Right now, the latter seems more likely. Happy holidays, all.