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Global warming science is still evolving — but not in the direction the disinformers think

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Issue date: 
September 5, 2010
Publisher Name: 
Climate Progress
Simon Lewis
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The WSJ pushed a new meme in its editorial, “Climate of Uncertainty:  Global warming science is still evolving; will future IPCC reports reflect that?“  Ironically, if the WSJ actually followed the scientific literature, rather than the disinformation campaign’s twisted version of it, they would know that global warming science is indeed evolving away from the 2007 IPCC report — but not in the direction they think.

In a AAAS presentation this year, William R. Freudenburg of UC Santa Barbara discussed his research on “the Asymmetry of Scientific Challenge”: New scientific findings are found to be more than twenty times as likely to indicate that global climate disruption is “worse than previously expected,” rather than “not as bad as previously expected.” You can see a review of many of the most important such studies here:  “An illustrated guide to the latest climate science.”

Since the WSJ piece bases part of its conclusion on research into the Amazon rain forest’s vulnerability to drought, I asked forest science expert Simon Lewis for a comment, since he has written widely on this subject (see Scientists: “There are multiple, consistent lines of evidence from ground-based studies published in the peer-reviewed literature that Amazon forests are, indeed, very susceptible to drought stress”).

What follows is Lewis’s reply:

A bizarre Wall Street Journal editorial published this week asks, ‘Global warming science is still evolving; will future IPCC reports reflect that?’ And ends, ‘… our understanding of how our climate works is still evolving. Is it too much to ask the climate establishment to acknowledge as much?’

So has the IPCC been hiding the evolution of scientists’ knowledge of climate change? Let’s take a single example, the detection of 20th century climate change and its possible attribution to human activities.

What do the IPCC say?

First, scroll back to 1990 and the very first IPCC Summary for Policymakers document:

We are certain of the following: Emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases: carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth’s surface.

Our judgment is that: Global mean surface air temperature has increased by 0.3 to 0.6°C over the last 100 years, with the five global-average warmest years being in the 1980’s.

The size of the warming over the last century is broadly consistent with the prediction by climate models, but is also of the same magnitude as natural climate variability….  The unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more.

So … a mechanism, some evidence, far from conclusive, with highlighted major uncertainties.

And the 1995 Assessment Summary for Policymakers:

Global mean surface air temperature has increased by between about 0.3 and 0.6°C since the late 19th century; the additional data available since 1990 and the re-analyses since then have not significantly changed this range of estimated increase.

More convincing recent evidence for the attribution of a human effect on climate is emerging from pattern-based studies, in which the modelled climate response to combined forcing by greenhouse gases and anthropogenic sulphate aerosols is compared with observed geographical, seasonal and vertical patterns of atmospheric temperature change. These studies show that such pattern correspondences increase with time, as one would expect, as an anthropogenic signal increases in strength. Furthermore, the probability is very low that these correspondences could occur by chance as a result of natural internal variability only. The vertical patterns of change are also inconsistent with those expected for solar and volcanic forcing.

Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors. These include the magnitude and patterns of long-term natural variability and the time-evolving pattern of forcing by, and response to, changes in concentrations of greenhouse gases and aerosols, and land surface changes. Nevertheless, the balance of evidence suggests that there is a discernible human influence on global climate.

Some evolution of understanding, along with uncertainties reported….

And the 2001 Assessment Summary for Policymakers:

The global average surface temperature has increased since 1861. Over the 20th century the increase has been 0.6 ± 0.2°C.

There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.

Still evolving, still some uncertainty….

And in 2007 assessment Summary for Policymakers:

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

The updated 100-year linear trend (1906 to 2005) of 0.74°C [0.56°C to 0.92°C] is therefore larger than the corresponding trend for 1901 to 2000 given in the TAR of 0.6°C [0.4°C to 0.8°C].

Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.

Contrary to the WSJ editorial, the IPCC reports do show an evolution of climate-related science. And they’ll certainly do so in the Fifth Assessment Report, indeed how could it be any different, the assessment being merely a review of the published literature.

Curiously, Anne Jolie the journalist who wrote the piece chose my area of research to illustrate her point, writing:

Also, last month, New Phytologist published a series of papers examining the Amazon rain forest’s vulnerability to drought, following years of increasingly dire predictions that anthropogenic carbon emissions and global warming will kill off Amazon trees. Climatologist Peter Cox, a co-author on four of those papers, told us, “One of the things that turns out to be important is the extent to which tropical forests respond positively to CO2 increases.”

The specifics of that relationship remain “a key uncertainty,” Mr. Cox said, and recent findings have raised more questions than they’ve answered. But the fact that higher CO2 levels can make plants more efficient at using water means that not only might rain forests survive CO2-induced drought better than previously thought, but that carbon emissions overall might even be good for rain forests, up to a point. That’s news, even if it has been little reported.

This is not a fair summary of research in the area on two counts. First, the editors of the New Phytologist special issue take a very different view on the future of Amazonia concluding, “Overall, a growing body of data is showing that Amazonian rain forests are highly (and negatively) responsive to strong, and especially extended soil moisture deficit, in terms of aboveground and belowground processes, net ecosystem production (NEP) and mortality.” They continue, “… when the expected feedback between vegetation and climate are combined with fire incidence and land-use change scenarios, we conclude that Amazon rain forests are highly vulnerable to loss during the coming decades.”

This is hardly a major reversal of previous results as the WSJ assert, nor “better than previously thought”.

Second, Prof. Cox’s groups’ latest paper modelling Amazon dieback clearly shows that the CO2 response of trees is important – nobody would disagree, or has, over the past decade since Prof. Cox’s first dieback paper was published.

Carbon dioxide fertilisation is not news, nor little reported. I had a paper published in Nature last year showing how well undisturbed rainforests are doing under recent climatic conditions, covered by CNN and many other news outlets.

Indeed, prior to that it was well covered in its own sub-section by IPCC Working Group I in its 2007 report.

The reality is that the response of tropical trees to rising temperatures, rising atmospheric CO2 and changes in rainfall in the dry season (if such changes occur) in the context of direct human impacts including selective logging, forest clearance and forest fires is complex. The only sensible response to this is investment in collecting data to reduce uncertainties, and getting teams of experts to write reviews of the literature to synthesis knowledge. This is just what the New Phytologist special issue and IPCC reports are doing. Yet rather than careful explanation of the science, we get a partial view to suit a political agenda.

But there is a further disturbing aspect to this. I asked Peter Cox what he thought about the WSJ article. He was surprised that he featured in a climate science bashing editorial. While his quotes were correctly transcribed Prof Cox was not told that the article was about attacking climate science. The same journalist tried the same sleight-of-hand with me over a potential Amazongate article. So memo to scientists. If Anne Jolis of the WSJ contacts you, watch out, or you could find yourself being tricked into starring in an article about scientists not being open and honest.


Extpub | by Dr. Radut