By 2047, Coldest Years will be Warmer than Hottest in Past

Local Editor

If greenhouse emissions continue their steady escalation, temperatures across most of the Earth will rise to levels with no recorded precedent by the middle of this century, researchers said Wednesday.

Scientists from the University of Hawaii at Manoa calculated that by 2047, plus or minus five years, the average temperatures in each year will be hotter across most parts of the planet than they had been at those locations in any year between 1860 and 2005.
To put it another way, for a given geographic area, "the coldest year in the future will be warmer than the hottest year in the past," said Dr. Camilo Mora, the lead scientist on a paper published in the journal Nature.

Unprecedented climates will arrive even sooner in the tropics, Mora's group predicts, putting increasing stress on human societies there, on the coral reefs that supply millions of people with fish, and on the world's greatest forests.
"Go back in your life to think about the hottest, most traumatic event you have experienced," Mora said in an interview. "What we're saying is that very soon, that event is going to become the norm."

The research comes with caveats. It is based on climate models, huge computer programs that attempt to reproduce the physics of the climate system and forecast the future response to greenhouse gases. Although they are the best tools available, these models contain acknowledged problems, and it is not clear how accurate they will prove to be at peering many decades ahead.

The models show that unprecedented temperatures could be delayed by 20 to 25 years if there is a vigorous global effort to bring emissions under control. While that may not sound like many years, the scientists said the emissions cuts would buy critical time for nature and for human society to adapt, as well as for development of technologies that might help further reduce emissions.

Other scientists not involved in the research said that slowing emissions would have a bigger effect in the long run, lowering the risk that the climate would reach a point that triggers catastrophic changes. They praised the paper as a fresh way of presenting information that is known to specialists in the field, but not by the larger public.

"If current trends in carbon dioxide emissions continue, we will be pushing most of the ecosystems of the world into climatic conditions that they have not experienced for many millions of years," said Ken Caldeira, a climate researcher at the Carnegie Institution for Science in Stanford, Calif.

The Mora paper is a rarity: a class project that turned into a high-profile article in one of the world's most prestigious scientific journals.

Source: NY Times