Mass Extinction #6

One of these days I should go back and take a look at the details of the first 5 mass extinctions. The last one was 65 million years ago, and the evidence for it being caused by a large impactor is pretty solid. The other ones are less clear, as far as I know. The sixth one is currently underway, and the cause is pretty clear. Joe Romm has a nice post about it [LINK]. Whenever reading Romm, one must remember that he's always presenting the worst case scenario (and as if it is inevitable), but even when one scales his arguments by 50% or so, it's not a pleasant picture. If anyone wants to skip the commentary and read the source material, it is a special issue of Phil. Trans. [LINK].

Coffee forests threatened by climate change impacts

This is serious. At least superficially similar to the pine beetles infecting forests in the Rockies, there's a pest called the coffee berry borer beetle that is infecting coffee plants around the world [LINK]. As the climate is changing, these beetles have started to become common pests in regions where they have historically been virtually unknown, such as Ethiopia. This insect problem just makes the impacts on coffee production worse, as there are already some issues with temperature sensitivity in growing coffee. Frankly, this story completely freaks me out, as I rely on coffee for survival.

Impact in North America?

There's been a lot of talk about an extraterrestrial impact in North America about 11,000 years ago. The idea is that such an event could have contributed to the extinction of North America's megafauna, like giant ground sloths and wooly mammoths. A new paper in PNAS by Haynes et al [LINK] examine the evidence from several "Clovis" sites. These are sites where remains of the Clovis people [wikipedia] have been found. Their analysis finds no strong evidence of an extraterrestrial impactor, and especially damning to me is that they find no enhancement of Iridium, which is a fingerprint for impacts.

While they are careful to say that they haven't ruled out an impact, I think this is strong evidence that the other hypotheses (e.g., human hunting) are more likely to have led to the megafaunal extinction.

Displacing world leaders from their comfort zones

Just read an interesting article about plans for the upcoming UN summit on climate change in Copenhagen [LINK]. Apparently the world leaders in attendance will be stripped of their entourage and be allowed just a single aide. That aide should be their country's environment minister, or equivalent. They will be put into small groups to talk about climate change and its impacts, pairing high-emission countries with those feeling the impacts. They will dine with activists and corporate executives. The idea is to get these leaders out of their political bubbles and force them to think about the effects of climate change in human terms (dare I say in ethical terms?). This seems like a great idea. I wish that the summit were longer, and that this kind of immersion therapy could be extended for several days. Removing the physical and artificial barriers of distance and isolation does wonders for thinking about a topic, and I have some hope that this will spur more urgent action. (Then I'll go back to being cynical when, e.g., the USA congress starts bickering about jobs and fairness and postpones actual action.)

The warming arctic

Over the past week or so, I've noticed a number of articles and posts about the Arctic. There seems to be some kind of ongoing flap about some climate change deniers denying that the extreme north is warming. I have (mostly) avoided reading those original posts because they can't be a good use of time (one example will essentially prove my point). Following each denier rant seems to be a barrage of posts refuting their claims. The good things about these posts are that they more carefully present evidence to support themselves and the reader can actually learn something from them (here's a good example from Tamino). Unfortunately, I don't think these posts help to convince the public of the state of the science, since the public doesn't read them (sorry, but they don't). If a person is willing to dig into the climate change issues enough to read these posts, I think they have already decided what they believe before they get involved (even passively) in these "debates." (They are, of course, not debates at all.)

Another article from the NYTimes.com helps explain why the warming Arctic is an important issue, not just for climate research, but for geopolitical and economic reasons. A commercial ship is about to finish traversing the Northeast Passage from South Korea to the Netherlands. This cuts thousands of miles off the usual trip. If more ships start going this way during the summer, Russia stands to profit because the ships will sail through Russian waters. The path has historically been blocked by ice even in the summer, but as the Arctic has warmed, summer ice has become reduced in area and thickness, and over the past few years the Northeast Passage has been open for a few weeks each year. Similarly the Northwest Passage through Canada's many islands has been open, but so far commercial ships haven't used it yet (they will soon, I would wager). These are impacts of climate change, and unlike most other impacts, these ones could be interpreted as positive for some of the involved parties. Of course, along with these routes opening, the open waters spell doom for the polar bears who have become unwitting symbols of the ecological impacts of a warming world.

On the research side of things, the warming Arctic has long been considered the proverbial canary in the coal mine. Because of strong positive feedbacks associated with snow and ice retreat and atmospheric water vapor, there has emerged a general understanding of the polar regions (especially in the north) as being particularly sensitive. The poles are expected to warm most rapidly, an effect usually called "polar amplification." There is some scientific uncertainty about whether the amplification is observed yet (e.g., this RealClimate post from C. Bitz), but there is strong consensus among researchers that it will emerge from the noise. This view is supported by climate modeling experiments, in which all the reliable models predict an amplified response in the Arctic. From my reading, which is incomplete, this extends to the Antarctic, but only on slightly longer timescales because of the heat transfer into the Souther Ocean.

Did the rain in Spain fall mostly on the plain, grandma?

A study about precipitation patterns in the Mediterranean region finds that there is a ubiquitous decrease [LINK]. The news article doesn't totally make sense, though, giving a mish-mash of half facts and ill-considered sentences. Maybe it's a poor translation? The figure caption is still in Spanish. The article gives the lead author and the journal, so I go to the GRL website to find the paper, and no, it isn't there. I search the web, finding the same news article over and over, "published" all over the internet, but no additional information.

I did find a very similar paper in the International Journal of Climatology, which would makes sense for this kind of study [LINK]. It's by the same author and was published in May. The difference is that this paper examines a set of precipitation indices, which I assume are based on rain gauges around the Iberian Peninsula, while the purported GRL article uses observations and the IPCC/PCMDI database of climate models. I'm not going to go into any detail on either paper, because I can't find the one that I want to see and because the one I did find doesn't seem to add any new information to the picture of decreasing precipitation in Iberia.

The topic can wait until I can get my hands on a proper analysis, but the bottom line is that there are observed changes in the precipitation across the Iberian Peninsula, especially southern Spain. This is also one of the regions that basically all the models agree will be severely impacted in the future, bringing persistent drought as global warming progresses. It's actually a pretty startlingly robust result, and is being borne out by observations. The pattern does extend across the Mediterranean, including southern France and northern Africa. The expectation is that warming will be greater in the region, and precipitation will decrease, and given the population and history of the region, I think it will prove an interesting result of climate change.

It's not just about polar bears

I just sat down to have a quick look at some of the (too many) RSS feeds I subscribe to, and I clicked on ClimateArk.org, which is essentially an environmental news aggregator. Five headlines appeared in my Google Reader screen. They highlight one of the directions that seems more and more relevant to climate science and policy: regional impacts of climate change. As the entire planet warms slightly, there will be substantial, life-altering changes to some regions, while others will be largely unaffected. Well, at least not as directly affected as some. Understanding these regional variations and predicting where they will occur and estimating the impact of changes in the physical system to ecosystems and populations is an emerging science. Even with relatively well-understood effects, like decreasing snow cover and melting permafrost in the far north, have unknown consequences (like understanding how much methane will be released when the permafrost melts).

The articles that came up on ClimateArk.org show some additional examples. First, form the Senate Foreign Relations Committee held hearings about how climate change will impact national security. Essentially, this is an example of how regional climate change will amplify unstable political situations around the world by stressing food and water supplies, changing coastlines, and shifting weather patterns. Second, a study coming out of the University of Colorado and CIRES assesses the water supply in the Colorado River Basin, and the authors suggest that persistent drought associated with climate change could lead to severe water shortages in the basin, which supplies water to some 30,000,000 people. This article reminded me of Brian Fagan’s interesting book “The Great Warming,” which looked at the so-called Medieval Warm Period and the rise and fall of societies around the world. One of the take-home messages of that book was that a little warming isn’t too bad for a lot of societies, but persistent drought destroys them. The third news item that was sitting on the top of the ClimateArk.org feed was covered by two articles, and is about crops in California’s central valley. A UC Davis study finds there has been a decrease in the “chilling hours” that cropland experiences, and several important crops rely on this cold winter weather. I would venture to guess that this regional effect is partly due to land use change and partly due to global warming, but that is just a guess. The important thing is that this becomes a serious concern to the food supply for the whole country, and many other countries, not to mention that California’s economy had long depended on agriculture. If crops start to falter in California, it really could have a destabilizing effect on the national economy and will impact jobs (agriculture, packing, shipping) and food supply and prices.

It’s also worth noting that two of the above articles contain sentences that say something like, “climate change isn’t just about polar bears, it’s about security.” In the first it is national security and in the last food security.

Are we all going to burn?

Well, if the USA Senate has anything to say about it, we'll all sit and burn coal until we choke on the carbon dioxide floating in the atmosphere. Today the Senate "mothballed" the Waxman-Markey legislation until September [LINK]. Why? Because so-called moderate democrats in the Senate want to make themselves look important. To who? I have no clue, but they claim to be sticking up for farmers and electricity consumers. This is bunk.

This politicization of global climate change is threatening, now more than ever, to doom our entire society to multiple generations of increasing temperature, more extreme weather events, and dramatic alterations to the pattern of rainfall. Not just in far away places, but in regions all across the United States. I'm not just being alarmist here, there is published evidence of the effects already being measurable along with strong evidence that the longer we continue to burn fossil fuels at the present rate, the more irreparable damage is done to the climate system. Examples of recent reports you can take a look at include the new Global Climate Change Impacts in the United States, Ecological Impacts of Climate Change (2009), Global Climate Change and Extreme Weather Events: Understanding the Contributions to Infectious Disease Emergence: Workshop Summary (2008), and the IPCC synthesis report. I'm happy to provide individual studies that support the findings of these reports as well, but they are generally easily found in the report bibliographies.

More coverage of the Carteret Islands

In the NYTimes.com today (slash yesterday) there's a story about the disappearing Carteret Islands by NEIL MacFARQUHAR. Again the article paints the sea-level rise in the Carteret Islands as a product of global warming, but I remain very skeptical of the assessment. I still haven't seen a reasonable attribution study about these islands, and the rate of sea-level rise there seems at odds with the small global trend.

Climate change refugees

George Monbiot says that about 2,600 people are evacuating from Carteret Islands in the tropical west Pacific. He attributes the evacuation to three things, mostly sea-level rise, but also the removal of mangroves and local volcanic activity. The sea-level rise apparently is manifest as high tides in springtime, which flood the very low atoll. The YouTube video below appears to corroborate the view that sea-level rise is pushing these people from their homes.

I don't have any real knowledge of this situation, but I have to admit that I am skeptical that this "sea-level rise" is due to global warming. There certainly has been measured sea-level rise, and some regions are likely to be harder hit than others, but the video appears to suggest this atoll has been cut into two by rising water, and the shoreline has receded by tens of meters (reportedly in just a few years). This does not suggest the kind of sea-level rise expected globally. The wikipedia page for the Carteret Islands also imply that there is not much evidence for this being a result of global warming, pointing out other influences that might be deleterious to the atoll, including normal erosive processes, isostatic adjustment, and use of dynamite fishing. If anyone knows of a true attribution study, that would be great, but until I see one, I am working under the assumption that this migration is probably related to human activities, but unlikely to be strongly related to global warming.

Melting glaciers, changing rivers

Well, in another blatant theft from DeSmogBlog, I bring you Jeanne Roberts' article about glaciers in the Swiss-Italian Alps melting. The interesting part of this article is not just that the glaciers in Europe are melting, this is really old news by now, but actually that the Swiss and Italian governments are implicitly acknowledging -- and I dare say adapting to? -- climate change by renegotiating their border. Yeah, two countries are talking about how to redefine their border without bothering to send a bunch of kids to their horrible dismemberment and death. 

The importance of the melting glaciers is clear for countries like Switzerland, which are landlocked and use mountain runoff for freshwater. The melting glaciers provide a lot of fresh water to streams and rivers, that is then used for the human population of those countries. In a glacier-free Europe, that source of water is gone, and countries will have to rely solely on seasonal snowpack melting. This isn't a great strategy, though, since the melt season is getting longer and longer, and seasonal snowpack is quite variable. Essentially the absence of the glaciers will add a level of instability to the water resources of interior Europe.

It is also worth noting that this story comes on the heels of a scientific paper about changing streamflow made waves two weeks ago. The paper is by Dai et al., and is in the upcoming issue of Journal of Climate. Some of the news coverage of the paper was a bit out of control. The paper is a compilation of data sets from around the world, measuring streamflow in large rivers. The main point of the paper is to show the basic results of the combined data set, and to provide a climatology to other researchers who want to know how much freshwater is going from the land into the oceans. You wouldn't have gotten that from the media coverage, much of which seemed to focus on the Colorado river, which isn't even mentioned in the paper by name. The headline grabbing aspect of the paper is a cursory examination of the trends in the data. Freshwater input into all the ocean basins except the Arctic show a decrease in overall streamflow, while the Arctic has an increase. It is not clear from my reading of the paper that these trends are (1) statistically significant or (2) attributable to climate change. The first point will be cleared up over the next couple of years as more people look at the statistics of this and other data sets. The second point will hopefully be better accounted for in future studies by trying to explicitly incorporate human-made changes in streamflow (for agriculture and including building dams and resevoirs). In the meantime, it is an interesting data set, and could have important implications for budgets of freshwater flux to the oceans. Whether the rivers are drying up remains an open question, and one that a lot of us are very interested in. 

Great animation about climate change

Wake Up, Freak Out - then Get a Grip from Leo Murray.


Wake Up, Freak Out - then Get a Grip from Leo Murray on Vimeo.

I saw this posted on Grist, and thought it was pretty cool.

I'm not a fan of the "tipping point" argument, actually. Not that I don't believe there are tipping points, but just because I don't know how to really quantify the risk they pose. We don't know where the tipping points are, but we do know about the mechanisms of adverse amplifying feedbacks in the climate system that could introduce these tipping points. I'm interested in the physical processes, and trying to quantitatively understand their impact on the climate system.

Endangered Species Act to be undermined by new rules

This is outrageous. The Bush administration is trying to introduce some kind of executive rule that would allow federal agencies to conveniently ignore the impact of projects on endangered species. Not only that, but the new rule would apparently ban federal agencies from assessing the greenhouse gas emissions from projects. You need to go read the story, there's one at Yahoo!. There are some additional reactions at gristmill.

I suppose that some might believe this argument that the current system is bloated and that federal agencies really can do their own assessments. However, the idea of independent review is so fundamental to science, and is so successful, that to just throw it aside for an intrinsically flawed self-evaluation system seems ludicrous to me.

We'll see how this plays out. Whether my paranoid, leftist brain is overpowering my rational, pragmatic one will come clear in the coming weeks and months.

Impact of warming on insects and other ectotherms

There has been quite a lot of press coverage of a new paper in PNAS (doi:10.1073/pnas.0709472105) by Deutsch et al. about how global warming might affect land-based invertebrates. The paper is very short, and easy to understand, so I recommend it. It's actually a simple idea, based on empirically derived "fitness curves" for different organisms. As I read it, the story comes down to the fact that tropical temperatures don't vary much during the course of the annual cycle, while at higher latitudes it does. This has affected the organisms that live in these different climate regimes; tropical organisms have come to "expect" a small temperature variance, and don't do well when the temperature changes more than normal. Organisms from places with distinct seasons are more amenable to temperature swings. This has been derived empirically as these fitness curves, which are broad for extra-tropical organisms and narrow for tropical ones. An interesting characteristic is that the maximum fitness level comes at a temperature optimum, followed by a precipitous decline. So Deutsch and co-authors followed up on this, defining a "warming tolerance" and a "thermal safety margin," which just measure how close an organism lives to its maximum temperature tolerance and to it's optimal temperature, respectively. Then they apply a warming scenario to see what happens, and it turns out that tropical insects (the data they used), get pushed really hard compared with midlatitude insects. This is somewhat surprising, since the tropics don't warm as much as higher latitudes, but because the tropical organisms live so close to their maximum temperature already, they are heavily stressed by the more moderate warming. They extrapolate to a global scale of impact on insects, and then three extra classes (lizards, frogs, turtles). This part of the paper does not seem surprising after the initial analysis, though the extension to lizards, frogs, and turtles helps deliver the message.

We often hear about the impact of climate change on biology, ecosystems, etc., but we don't often see such a concise and simple, yet far-reaching and quantitative analysis of "impact." This paper stands out to me because of these traits, and gives an excellent example to use when discussing the importance of climate change beyond temperature, precipitation, etc.