The Wall Street Journal is reporting that the new Intergovernmental Panel on Climate Change’s (IPCC) “fifth assessment report,” will slightly dial back its predictions of how much the planet will warm over the coming decades.
Outside of the numbers, there appears to be an acknowledgement — finally — that there has been a significant pause in warming trends and that climate sensitivity to CO2 may have been overestimated.
The lower predictions are slight, but significant, says Matt Ridley, author of the article:
Specifically, the draft report says that “equilibrium climate sensitivity” (ECS)—eventual warming induced by a doubling of carbon dioxide in the atmosphere, which takes hundreds of years to occur—is “extremely likely” to be above 1 degree Celsius (1.8 degrees Fahrenheit), “likely” to be above 1.5 degrees Celsius (2.4 degrees Fahrenheit) and “very likely” to be below 6 degrees Celsius (10.8 Fahrenheit). In 2007, the IPPC said it was “likely” to be above 2 degrees Celsius and “very likely” to be above 1.5 degrees, with no upper limit. Since “extremely” and “very” have specific and different statistical meanings here, comparison is difficult.
Still, the downward movement since 2007 is clear, especially at the bottom of the “likely” range. The most probable value (3 degrees Celsius last time) is for some reason not stated this time.
A more immediately relevant measure of likely warming has also come down: “transient climate response” (TCR)—the actual temperature change expected from a doubling of carbon dioxide about 70 years from now, without the delayed effects that come in the next century. The new report will say that this change is “likely” to be 1 to 2.5 degrees Celsius and “extremely unlikely” to be greater than 3 degrees. This again is lower than when last estimated in 2007 (“very likely” warming of 1 to 3 degrees Celsius, based on models, or 1 to 3.5 degrees, based on observational studies).
Most experts believe that warming of less than 2 degrees Celsius from preindustrial levels will result in no net economic and ecological damage. Therefore, the new report is effectively saying (based on the middle of the range of the IPCC’s emissions scenarios) that there is a better than 50-50 chance that by 2083, the benefits of climate change will still outweigh the harm.
The benefits of a slightly warming earth are critical when you consider that an increase in arable lands in the north would mean we’d be able to feed increased populations:
Warming of up to 1.2 degrees Celsius over the next 70 years (0.8 degrees have already occurred), most of which is predicted to happen in cold areas in winter and at night, would extend the range of farming further north, improve crop yields, slightly increase rainfall (especially in arid areas), enhance forest growth and cut winter deaths (which far exceed summer deaths in most places). Increased carbon dioxide levels also have caused and will continue to cause an increase in the growth rates of crops and the greening of the Earth—because plants grow faster and need less water when carbon dioxide concentrations are higher.
Up to two degrees of warming, these benefits will generally outweigh the harmful effects, such as more extreme weather or rising sea levels, which even the IPCC concedes will be only about 1 to 3 feet during this period.
Explaining the “pause” in warming has become a “cottage industry” says Ridley:
It is now more than 15 years since global average temperature rose significantly. Indeed, the IPCC chairman Rajendra Pachauri has conceded that the “pause” already may have lasted for 17 years, depending on which data set you look at. A recent study in Nature Climate Change by Francis Zwiers and colleagues of the University of Victoria, British Columbia, found that models have overestimated warming by 100% over the past 20 years.
Explaining this failure is now a cottage industry in climate science. At first, it was hoped that an underestimate of sulfate pollution from industry (which can cool the air by reflecting heat back into space) might explain the pause, but the science has gone the other way—reducing its estimate of sulfate cooling. Now a favorite explanation is that the heat is hiding in the deep ocean. Yet the data to support this thesis come from ocean buoys and deal in hundredths of a degree of temperature change, with a measurement error far larger than that. Moreover, ocean heat uptake has been slowing over the past eight years.
The most plausible explanation has always been that the scientists have simply been wrong — that their flawed models and questionable methodologies gave the wrong answers to legitimate scientific questions. The problem is that change in the consensus won’t come overnight. In the meantime, governments will ignore this gradual walk back by the IPCC and continue to act as if the world will end unless we give them control of the world’s economies.
Others are ignoring the lowered temperature predictions and are latching on to other aspects of the report that feed the hysteria. There so many who have so much invested in the theory of catastrophic climate change that it isn’t likely the meme will disappear any time soon.
But if the IPCC keeps reducing its predictions of rising temperatures, the hysterics will find themselves on the outside looking in.
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