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Experts: A two-degree global temperature increase is still too much; UN needs lower target

Since 1996, the EU has recognized 2⁰C as the maximum allowable global temperature increase by 2100 – anything more would be catastrophic. Since then, reams of legislation have been written with this as a target. Now, there’s only one small problem – two thirds of the countries who agreed to the target have come to the conclusion that 1.5⁰C is a more realistic number if we would hope to avoid irreversible damage. Petra Tschakert, a climatologist from Penn State University, discussed the changes in copious detail at the latest Conference of the Parties (COP20) meeting in Lima, Peru. Her structured expert dialogues have been published in the journal Climate Change Responses.

“Best evidence, though, comes from terrestrial ecosystems, suggesting significant differences in projected risk between 1.5°C and 2°C, especially in the Polar Regions, high mountain areas, and the Tropics. As for coral reefs, a temperature rise capped at <1.5°C would be needed to protect at least 50% of all existing coral reefs. From the perspective of human and agricultural systems, the difference between a 1.5°C and 2°C global temperature increase is distinctly more difficult to assess as global average conditions become fuzzy when applied to local levels where impact studies are most abundant,” said Tschakert.

The seemingly arbitrary 2⁰C actually has roots in the 1960s and 70s, when climatologists figured that a doubling of the then-current atmospheric CO2 levels would result in a 2⁰C increase. That number incorporates data from pre-industrial times, and for reference the average global temperature has already risen about 0.85⁰C since the industrial revolution.

The 2⁰C figure was a feature in policy debates from then on, and by 2009 it was ratified as an official global target for greenhouse gas emission reductions at the COP15 in Copenhagen in 2009. Since then, a whopping 70% of participating countries have come to the conclusion that 2⁰C would be unsafe for their communities. Many of these countries are low- and middle-income nations near the equator (Caribbean nations in particular), who are more likely to feel the effects of even small changes in the average global temperature.

For now, though, the Intergovernmental Panel on Climate Change (IPCC) is nowhere near revising their climate change targets. Instead, they’re arguing over lines on a graph.

“Moreover, fierce debates erupted over the visual highlighting of certain temperature targets in the graphic. The draft version of the figure included two dotted horizontal lines, one at 2°C and the other at 4°C. Again, St. Lucia, supported by Dominica, Jamaica, Tuvalu, Cuba, Mali, France, and then also Germany, requested a third dotted line at 1.5°C, arguing that this line would be highly policy-relevant. Yet, others considered it policy-prescriptive and hence inappropriate for the IPCC whose mandate it is to be no more than policy-relevant,” Tschakert wrote.

So, here we are. Many countries argue that the .5⁰C difference could be more significant than it sounds, but the UN is nowhere near revising their policy just yet.