No more planet as we know it? Unless world abolishes carbon emissions a lot faster, temperatures are 90 percent likely to rise by 2 to 5 degrees Celsius by 2100, new study warns
Ruth Schuster Aug 03, 2017

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According to new research published in Nature Climate Change, the terrifying predictions of the Intergovernmental Panel on Climate Change are too tame.

In Israel, July temperatures were up to 2.5 degrees more than the average for that month. Australia reported average maximum temperatures 2.6 degrees above the long-term average and Alaskans are sweltering. And it will get worse, warns the statistic-driven study.

By the year 2100, the global temperature is 90 percent likely to increase by 2.0 to 4.9 degrees Celsius above pre-industrial levels, says the new study. The median calculated increase is 3.2 degrees Celsius (5.8 Fahrenheit).

There is only a 5 percent chance that global temperatures will increase by less than 2 degrees. The chance of an increase below 1.5 degrees is 1 percent, according to the new calculations in the paper, and “less than 2 degrees warming by 2100 is unlikely.”

On the present trajectory of global population growth and economics, the global climate is likely to heat up so much that the planet can never recover, the scientists warn, including because of mass species extinctions.

Keeping global warming less than 2 degrees on average will be impossible unless the world gets serious about decarbonization: halting all activity that produces carbon emissions. Even that increase of 2 degrees (3.6 degrees Fahrenheit) would make things extremely uncomfortable.

Warming by “only” 2 degrees by 2100 doesn’t mean more splashing around at the beach. Heat is associated with more than violence, mosquitoes and insomnia. NASA itself has warned that a 2-degree increase will likely spell widespread starvation from crop failures, coastal disaster from sea-level rise, and the extinction of the world’s coral reefs (with the possible exception of Israel’s reef in the Red Sea, which has evolved to be peculiarly resistant to temperature fluctuations).

Creating a better apricot that produces fruit in relatively higher temperatures, or drought-resistant rice, won’t help if mid-day temperatures often pass the survivable, as has been predicted for the Middle East by the year 2100.

Helpfully, NASA has explained the difference between a 1.5 C rise and 2 C rise in temperature. With an increase of 1.5 degrees Celsius, the Mediterranean region is predicted is forecast to have about 9 percent less fresh water available. “At 2 C, that water deficit nearly doubles,” NASA wrote. Even under tame scenarios of carbon emissions, mid-day temperatures in the Middle East are likely to pass survivable levels.

“Our analysis shows that the goal of 2 degrees is very much a best-case scenario,” stated lead author Adrian Raftery of the University of Washington. “It is achievable, but only with major, sustained effort on all fronts over the next 80 years.”

The model the team built is based on solid data, not future carbon emission scenarios. They analyzed three trends: total world population, GDP per capita and “carbon intensity”, which means the amount of carbon emitted per dollar of economic activity.

One perhaps surprising result of their analysis is that the expected increase in global population, to around 11 billion, isn’t expected to change the trajectory of global warming much because most of the increase will be in Africa.

The forecasts by the team, from the University of Washington and University of California, are based on data for the years 1960 to 2010. Meanwhile, the years since 2010 have been some of the hottest in recorded history.

Keeping global warming less than 1.5 degrees Celsius means the world has to accelerate decarbonization compared with the recent past, and fast. The world must change its carbon emission patterns abruptly to keep the planet survivable. It still won’t be comfortable. Just to name one element, scientists are now predicting that the frequency of “extreme” El Niño events will double even in a 1.5 degrees Celsius increase, and will continues to ramp up long after global temperatures stabilize.

The good news is Raftery’s conclusion that the Paris agreement goals are ambitious but remain realistic, if the industrialized world pulls together, fast, to develop technologies that can sustainably and affordably replace carbon. The bad news, Raftery added, is that no steps are likely to be enough to achieve the target of keeping warming at or below 1.5 degrees. A separate study from the University of Colorado has concluded that even if all fossil fuel emissions were halted this year, global temperatures would very likely be 1.3 degrees Celsius higher than pre-industrial levels by 2100. It seems we’re cooked. The question is whether we’re done.
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