Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

As promised, we report here on yet another published estimate of the earth’s equilibrium climate sensitivity that is towards the low end of the United Nations’ Intergovernmental Panel on Climate Change (IPCC) range of possibilities.

Recall that the equilibrium climate sensitivity is the amount that the earth’s surface temperature will rise from a doubling of the pre-industrial atmospheric concentration of carbon dioxide. As such, it is probably the most important factor in determining whether or not we need to “do something” to mitigate future climate change. Lower sensitivity means low urgency, and, if low enough, carbon dioxide emissions confer a net benefit.

And despite common claims that the “science is settled” when it comes to global warming, we are still learning more and more about the earth complex climate system—and the more we learn, the less responsive it seems that the earth’s average temperature is to human carbon dioxide emissions.

The latest study to document a low climate sensitivity is authored by independent scientist Nic Lewis and is scheduled for publication in the Journal of Climate. Lewis’ study is a rather mathematically complicated reanalysis of another earlier mathematically complicated analysis that matches the observed global temperature change to the temperature change produced from a simple climate model with a configurable set of parameters whose actual values are largely unknown but can be assigned in the model simulations. By varying the values of these parameters in the models and seeing how well the resulting temperature output matches the observations, you can get some idea as to what the real-world value of these parameters are. And the main parameter of interest is the equilibrium climate sensitivity. Lewis’ study also includes additional model years and additional years of observations, including several years from the current global warming “hiatus” (i.e., the lack of a statistically significant rise in global temperature that extends for about 16 years, starting in early 1997).

We actually did something along a similar vein—in English—and published it back in 2002. We found the same thing that Lewis did: substantially reduced warming. We were handsomely rewarded for our efforts by the climategate mafia, who tried to get 1) the paper withdrawn, 2) the editor fired—not just from the journal, but from Auckland University, and 3) my (Michaels) 1979 PhD “reopened” by University of Wisconsin.

Read the rest of this post »

Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.

From the authors of a new paper just-published in the journal Nature Geoscience comes this surprising finding:

Tropical forests are less likely to lose biomass – plants and plant material – in response to greenhouse gas emissions over the twenty-first century than may previously have been thought.

A rare “not as bad as we thought” admission about the impacts of manmade global warming!

Not only that, but based on recent findings that the true climate sensitivity is much lower than climate models emulate—findings not incorporated in new study—the results are probably still even more “not as bad as they thought” than they thought!

Chris Huntingford from the U.K’s Centre for Ecology & Hydrology and colleagues coupled climate model projections to a land surface/vegetation model to see how the tropical forests in the Americas, Africa, and Asia respond to changes in atmospheric conditions. Their vegetation model includes interactions between terrestrial plants and influences such as temperature, precipitation, and the carbon dioxide concentration of the atmosphere (a plant fertilizer).

Unlike other studies which used a very limited selection of climate models and less sophisticated vegetation models, the Huntingford team found that in virtually all future simulations that the biomass of tropical forests increases over the course of the 21^st century. This is a significantly different result than many previous which suggested that anthropogenic climate change would lead to, as Huntingford et al. put it, “catastrophic losses of forest cover and biomass.”

Perhaps most interestingly, the major driver for the biomass increase is the projected growth in atmospheric carbon dioxide concentration (thanks to our use of fossil fuels). The model projected changes in precipitation had little impact on the biomass predictions and the projected increase in temperature acted to decrease the biomass (although not as much as additional carbon dioxide acted to increase it).

Which is why the results probably get even better if there is less warming associated with carbon dioxide emissions than current generation climate models predict (new research suggest that climate models together produce about 50% more warming than they should).

The authors are quick to mention that uncertainty abounds, as our level of understanding of forest response to changing environmental conditions is not all that high. But even given these uncertainties, the authors are confident that their results of increasing biomass are robust. Here is how Huntingford described the situation in a press release:

The big surprise in our analysis is that uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections. Despite this we conclude that based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas (Amazonia and Central America), Africa and Asia.

Resilience. A refreshingly honest assessment of an ecosystem response to climate change. And one that is probably a much more apt descriptor of natural systems than “delicate,” “sensitive,” or “fragile.”

Now if only the folks in charge of assembling national and international climate impact assessments would realize (or probably more accurately, admit to) this.

We are hard at work trying to focus their attention as we are vigorously reviewing the latest draft “National Assessment” of climate change.  We will leak out particularly juicy snippets in these pages when the time seems right.

Reference:

Huntingford, C. et al., 2013. Simulated resilience of tropical rainforests to CO2-induced climate change, Nature Geoscience, 10.1038/NGEO1741.

Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.” 

Today’s  global media are ablaze with coverage of newly reported scientific findings purporting to show that anthropogenic global warming is leading to more extreme weather events such as heat waves, forest fires, and floods.

The findings are being made available in the early releases section of the Proceedings of the National Academy of Sciences (PNAS) and represent the work of a group of researchers from the Potsdam Institute for Climate Impact Research (PIK)—an institute which can be routinely counted on to produce rather alarming climate change studies. The new analysis, led by Vladimir Petoukhov, is no exception. 

The researchers examined the trends in the daily patterns of air flow in the lower atmosphere and found that some patterns had become more persistent with time—a characteristic that leads to a slowdown in the forward motion of weather systems. Or as the researchers put it in their press release, “What we found is that during several recent extreme weather events these planetary waves almost freeze in their tracks for weeks.” To make sure you understand the implications, they added “Since many ecosystems and cities are not adapted to this, prolonged hot periods can result in a high death toll, forest fires, and dramatic harvest losses.”

While climate alarm plays well in the media, what doesn’t play so well is climate-as-normal.

Case and point: there are zero media stories about a similarly timed study purporting to show that any anthropogenic global warming influence on extreme weather events is too small to be reliably detected.

This study, available in the early-release section of the journal Geophysical Research Letters, was performed by the research team of James Screen and Ian Simmonds of the University of Melbourne. Screen and Simmons examined the trends in the daily patterns of air flow in the lower atmosphere and found little significant change. They note that “the changes in meridional amplitude over recent decades are relatively small compared to the year-to-year variability” and “that possible connections between [anthropogenic global warming] and planetary waves, and the implications of these, are sensitive to how waves are conceptualized.” They cautiously conclude that “[t]he contrasting meridional and zonal amplitude trends have different and complex possible implications for midlatitude weather, and we encourage further work to better understand these.”

[Layman’s translation: There are few significant changes in north-to-south extent of jet stream troughs or their forward speed. The data are so noisy that results are highly dependent upon what analytical method is chosen. The contrasting north-south and east-west changes in jet stream troughs have multiple influences that we haven’t sorted out yet, but it would be foolish to tie them to global warming at this time.]

Read the rest of this post »