Climate Letter #1055

An important new study sees an increase in the future sensitivity of temperature increases to increases in the CO2 level.  Sensitivity depends not just on the radiation blocking of CO2 alone but on the impact of all the various feedbacks from contemporary circumstances that are driven by the CO2 increase.  During the ice ages the albedo feedback from growing and shrinking ice sheets had every bit as much influence on temperature as CO2 and all other greenhouse gases, but that particular influence will be greatly diminished in the future.  The absence of that one effect implies much lower sensitivity in the future, but scientists are always on the lookout for other feedbacks, either positive or negative, that could arise because of warming due to the current CO2 expansion.  This study has found some which are tied to expected changes in cloud cover and other effects in the upper atmosphere which will combine to accelerate the amount of warming in the lower atmosphere.  This is not good news—“These results emphasize the importance of rapidly reducing human caused emissions of greenhouse gases to avoid the worst impacts from ongoing climate change.”  The study, which has been peer-reviewed and is supported by observations, appeared in a prestigious journal, thereby demanding a high level of attention.
–Added note:
A number of studies have been published in recent years suggesting that during ancient times when temperatures were known to be much higher than at present the concurrent level of CO2 in the atmosphere may have been only moderately higher than that which we have lately accomplished.  They have various ways of calculating what the true CO2 level may have been in the deep past, all of which are subject to a wide range of errors, but there is growing confidence that the range of errors is well on the way to being reduced.  Here is one such study which you can look at to see how they go about it, in this case concluding that CO2 stayed below 1000 ppm for at least the last 65 million years.
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The connection between deforestation, climate change and drought in Brazil.  Sao Paulo, with a population of 21 million, is not getting as much rainfall as it needs and is facing a real crisis.  Antonio Nobre, a climatologist at the Space Research Institute, calls the Amazon a “biotic pump” that provides the energy for “rivers in the sky” to flow thousands of miles to São Paulo. “Without this booster, he warns, the southeast of Brazil would likely be a desert like many other regions at the same latitude.”  (I.e., in southern Africa and Australia.)
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The clothing industry is seldom mentioned as a major contributor to climate change.  A new report says it “has created a business which creates greenhouse emissions of 1.2bn tonnes a year – larger than that of international flights and shipping combined.”  Statistics reveal it as “incredibly wasteful” and in need of a thorough overhaul.
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How often do volcanic super-eruptions occur?  A new study calculates a frequency that is quite a bit lower than most common estimates, with the new figure showing a most likely average of just 17,000 years.  Such an eruption, as defined, would wreak havoc on weather conditions for a number of decades.  There were two of these between 20 and 30 thousand years ago but none since on that scale.
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The cost of solar panels continues to plunge.  Joe Romm brings us some of the latest numbers.  It is all but guaranteed that the decline will continue and demand will accelerate as a consequence.
Carl
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