Ag Policy Blog

"Warming of the climate system is unequivocal," the U.N. Intergovernmental Panel on Climate Change stated in its first sentence to a report to policymakers on Friday.

The IPCC, as it is known, released its first report since 2007 on the science behind climate change. In its press release Friday, the IPCC stated at the top, "Human influence on the climate system is clear."

Such a report is another scientific breakthrough in modeling what will happen to the Earth's atmosphere, temperatures and weather volatility. But the report leaves everyone to answer for themselves, "What does this mean to me?"

The impact of climate change as the global population continues to rise should be a statement high in an IPCC report, but the scientists don't draw such understandable conclusions.

For agriculture, it should mean globally that weather will increasingly become more volatile.

Climate change is happening because of continued pumping of greenhouse-gases into the atmosphere driven by fossil fuels.

The scientists sought to dispel the argument advanced by some scientists and groups that temperature increases stopped in 1998. IPCC experts noted that 1998 was characterized by the second strongest El Nino year in the 20th century, which has a warming effect.

"Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1,400 years."

Adverbs fill the report, particularly "likely," "very likely" and "extremely likely." Adverbs create uncertainty when we hear or read them. For the scientists, though, the adverbs are shorthand "to indicate an assessed likelihood of an outcome or result." If a statement is "virtually certain," there's a 99-100 probability of the cause or outcome. If something is "extremely likely", then it's at 95% certain. "Very likely" is a 90% probability and "likely" is at least a 66% probability.

Some statements from the news release and summary to policymakers:

It is "extremely likely" that human influence has been the dominant cause of the observed warming since the mid-20th century. The warming that has already occurred is "unequivocal," the report states. "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia."

Heat waves are "very likely" to occur more frequently and last longer.

Global surface temperature change for the end of the 21st century is projected to be "likely" to exceed 2.2 degrees F (1.5.C) and fall in a range to as much as 8.6 degrees F (4.5 C). A lot has been made of the fact IPCC has lowered its floor from 3.6 F to 2.2 F in the 2007 report. As the IPCC stated, the lower temperature limit of is less, but the upper limit is the same.

It is "very likely" that the Arctic sea ice cover will continue to shrink and thin and that spring snow cover in the Northern Hemisphere will continue to decline as global mean surface temperature rises. Global glacier volume will further decrease.

Some people are going to continue to hang their arguments on the 5% uncertainty. Just last week, the Heartland Institute pre-empted the IPCC report with its own panel of 40 scientists who took the likelihood from climate models and concluded, “Scientists have not been able to devise an empirically validated theory proving that higher atmospheric CO2 levels will lead to higher global average surface temperatures."

To offer an analogy, the IPCC report is like telling a guy who builds his home next to the Missouri River that he should insure against the risk of a flood because there's a 95% likelihood that the house would end up underwater during the life of the loan. Heartland and others counter the risk with, "So you are telling me that there's a chance ..."

Friday's report was the first of four reports that will come from the IPCC over the next year.

A summary of the IPCC report can be found at http://dld.bz/…

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