An illustrated guide to the latest climate science

Here is an update of my review of the best papers on climate science in the past year. If you want a broader overview of the literature in the past few years, focusing specifically on how unrestricted emissions of greenhouse gas emissions are projected to impact the United States, try “An introduction to global warming impacts: Hell and High Water.”

I’m adding some of the best figures from those papers, too. For those who like their science delivered through videos, let me suggest the panel I hosted earlier this month, may I suggest Video and PPTs of “The Science of Climate Change” with Dr. Christopher Field and Dr. Michael MacCracken (which is the source of the above figure showing the decadal temperature trend, together with the annual temps).

In 2009, the scientific literature caught up with what top climate scientists have been saying privately for a few years now:

  • Many of the predicted impacts of human-caused climate change are occurring much faster than anybody expected — particularly ice melt, everywhere you look on the planet.
  • If we stay anywhere near our current emissions path, we are facing incalculable catastrophes by century’s end, including rapid sea level rise, massive wildfires, widespread Dust-Bowlification, large oceanic dead zones, and 9°F warming — much of which could be all but irreversible for centuries. And that’s not the worst-case scenario!
  • The consequences for human health and well being would be extreme.

That’s no surprise to anybody who has talked to leading climate scientists in recent years, read my book Hell and High Water (or a number of other books), or followed this blog. Still, it is a scientific reality that I don’t think more than 2 people in 100 fully grasp, so I’m going to review here the past year in climate science. I’ll focus primarily on the peer-reviewed literature, but also look at some major summary reports.

Let’s start with the basics. Heat-trapping greenhouse gases are at unprecedented levels, and the paleoclimate record suggests that even slightly higher levels are untenable:

Since we have record levels of heat-trapping gases, it’s not surprising that we also learned that this was the hottest decade in the temperature record and that the Arctic is the hottest in at least two millenia.

A Hockey Stick in Melting Ice

In two key papers, we learned that the planet is warming from those GHGs just where climate science said it would “” the oceans, which is where more than 90% of the warming was projected to end up (see “Skeptical Science explains how we know global warming is happening.”). The key findings in the second study are summed up in this figure:

Figure [2]: Time series of global mean heat storage (0–2000 m), measured in 108 Jm-2.

That study makes clear that upper ocean heat content, perhaps not surprisingly, is simply far more variable than deeper ocean heat content, and thus an imperfect indicator of the long-term warming trend.

Unexpectedly, even Antarctica appears to be warming:

This global warming is driving melting at extraordinary rates every where we look, including places nobody expected:

And given that unexpectedly fast ice melt, it’s no surprise the science now projects much higher and much faster sea level rise than just a few years ago:

We continued to learn about the dangerous positive carbon-cycle feedbacks that threaten to amplify the impacts of human-caused GHGs.

Indeed, the best evidence is that the climate is now being driven by amplifying feedbacks — see, most notably:

Using the first “fully interactive climate system model” applied to study permafrost, the researchers found that if we tried to stabilize CO2 concentrations in the air at 550 ppm, permafrost would plummet from over 4 million square miles today to 1.5 million. If concentrations hit 690 ppm, permafrost would shrink to just 800,000 square miles:

High emissions levels + positive feedbacks = climate catastrophe:

“This graph shows the percentage increase in area burned by wildfires, from the present-day to the 2050s, as calculated by the model of Spracklen et al. [2009] for the May-October fire season. The model follows a scenario of moderately increasing emissions of greenhouse gas emissions and leads to average global warming of 1.6 degrees Celsius (3 degrees Fahrenheit) by 2050. Warmer temperatures can dry out underbrush, leading to more serious conflagrations in the future climate.”

And the plausible worst-case scenario is even worse than this grim “business as usual” emissions case:

This is the “plausible worst case scenario” for 2060 from the UK Met Office that occurs in 10% of model runs of high emissions with the carbon cycle feedbacks [temperature in degrees Celsius, multiple by 1.8 for Fahrenheit]:

And this is not good news for human health and welfare

So the time to act is most certainly now.

I’ll end with the best piece of scientific news I wrote about, which suggests it is not too damn late to act — a NOAA-led study, “Observational constraints on recent increases in the atmospheric CH4 burden” (subs. req’d, NOAA online news story here), which found:

Measurements of atmospheric CH4 from air samples collected weekly at 46 remote surface sites show that, after a decade of near-zero growth, globally averaged atmospheric methane increased during 2007 and 2008. During 2007, CH4 increased by 8.3 ± 0.6 ppb. CH4 mole fractions averaged over polar northern latitudes and the Southern Hemisphere increased more than other zonally averaged regions. In 2008, globally averaged CH4 increased by 4.4 ± 0.6 ppb; the largest increase was in the tropics, while polar northern latitudes did not increase. Satellite and in situ CO observations suggest only a minor contribution to increased CH4 from biomass burning. The most likely drivers of the CH4 anomalies observed during 2007 and 2008 are anomalously high temperatures in the Arctic and greater than average precipitation in the tropics. Near-zero CH4 growth in the Arctic during 2008 suggests we have not yet activated strong climate feedbacks from permafrost and CH4 hydrates.

Woo-hoo!

Yes, early this year I reported that NOAA found “Methane levels rose in 2008 for the second consecutive year after a 10-year lull,” but so far that most dangerous of all feedbacks “” Arctic and tundra methane releases “” does not appear to have been fatally triggered.

The anti-science crowd use smoke and mirrors to distract as many people as possible, but the rest of us need to listen to the science and keep our eyes on the prize — reversing greenhouse gas emissions trends as quickly and rapidly as possible.

Please use the comments to add links to any major studies I didn’t cover here. I will be updating this post continuously.

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