Cli­mate change straight talk

Gov­ern­ment draft re­port says fac­tors driv­ing global warming are clear

Los Angeles Times - - NEWS - By Alexan­dra Zavis and Raoul Ranoa

The con­clu­sions con­tained in a draft fed­eral re­port on cli­mate change are un­equiv­o­cal: Hu­man-in­duced global warming is real, and left unchecked, the con­se­quences could be dire.

Although not new, the find­ings are at odds with claims by Pres­i­dent Trump and mem­bers of his ad­min­is­tra­tion, who con­tinue to as­sert that the ex­tent of the hu­man con­tri­bu­tion to cli­mate change is not clear.

In June, Trump an­nounced that the U.S. would with­draw from the agree­ment reached in Paris in 2015, in which nearly 200 coun­tries pledged to re­duce emis­sions of heat-trap­ping green­house gases, say­ing the deal was bad for the coun­try.

The re­port’s au­thors, how­ever, say the fac­tors driv­ing cli­mate change are quite clear.

“Many lines of ev­i­dence demon­strate that hu­man ac­tiv­i­ties, es­pe­cially emis­sions of green­house gases, are pri­mar­ily re­spon­si­ble for the ob­served cli­mate changes over the last 15 decades,” the au­thors wrote. “There are no al­ter­na­tive ex­pla­na­tions.”

The re­port, a syn­the­sis of the avail­able science pre­pared by 13 gov­ern­ment agen­cies, is part of the Na­tional Cli­mate As­sess­ment, which is man­dated by Congress and is sup­posed to be pub­lished ev­ery four years.

The lat­est draft has been ex­ten­sively re­viewed, and the au­thors are wait­ing for per­mis­sion from the Trump ad­min­is­tra­tion to re­lease the re­port to the public — which prob­a­bly ex­plains why it was leaked to the New York Times.

“We have not re­ceived any in­di­ca­tion yet that it is not on sched­ule for pub­li­ca­tion,” said Katharine Hay­hoe, a pro­fes­sor of po­lit­i­cal science at Texas Tech Univer­sity and one of the lead au­thors of the re­port. “But un­der­stand­ably there are fears that it won’t be ap­proved, or that it could be re­turned to the au­thors with sub­stan­tial changes that we might not be com­fort­able with be­cause they aren’t con­sis­tent with the science.”

The draft re­port con­cludes that av­er­age tem­per­a­tures over much of the world in re­cent decades have been much higher and have risen faster than at any time in the last 1,700 years. It is “ex­tremely likely” that more than half of the rise in global tem­per­a­tures since the mid-20th cen­tury was the re­sult of hu­man ac­tiv­ity, it says.

Even small tem­per­a­ture in­creases can have ma­jor ef­fects, such as more fre­quent droughts and ex­treme storms, melt­ing po­lar ice sheets and ris­ing seas.

Sci­en­tists have gen­er­ally hes­i­tated to at­tribute spe­cific weather events to cli­mate change. But the au­thors say there is now rel­a­tively strong ev­i­dence for a hu­man con­tri­bu­tion to events such as the heat waves in Europe in 2003 and in Aus­tralia in 2013.

Here are more of the find­ings con­tained in the draft re­port:

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