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Future global warming could be twice as warm as predicted by climate models under status quo scenarios and even if the world reaches 2 ° C, sea level could reach six meters or more, according to one International team The results published last week in Nature Geoscience are based on observational evidence of three warm periods over the past 3.5 million years, when the world was warmer by 0 , 5 to 2 ° C that research has also revealed that large areas of ice caps could collapse and that significant changes in ecosystems could see the Sahara Desert become green and the edges of the tropical forests turn into savannah dominated by fire. . "Observations from past warm-ups suggest that a number of amplifying mechanisms, poorly represented in climate models, increase long-term warming beyond the projections of the climate model," explains Professor Hubertus Fischer of University of Bern. This suggests that the carbon budget to avoid 2 ° C of global warming could be much lower than expected, leaving very little room for error to achieve the Paris targets. "
To obtain their results, the researchers examined three of the best … warm periods documented, the Holocene thermal maximum (5000-9000 years), the last interglacial (129,000-116,000 years) and the warm period of the Middle Pliocene (3.3-3 million years ago.) two periods were caused by predictable changes in the Earth's orbit, while the mid-Pliocene event was the result of atmospheric concentrations of carbon dioxide from 350 to 450 ppm, which is about the same as today.
Combination of a wide range of measurements kernels the researchers have reconstructed the I & # 39; climate change impact
the climate has stabilized, but today, our planet is heating up much faster than any of these times, as carbon dioxide emissions caused by humans continue to grow. Even if our emissions stopped today, it would take centuries or millennia to reach equilibrium.
The changes of the Earth in these past conditions were profound – there were substantial withdrawals of the Antarctic and Greenland icecaps and as a result the levels increased by at least six meters; marine plankton ranges have been reorganized to reorganize entire marine ecosystems; the Sahara became greener and forest species moved 200 km to the poles, as did the tundra; high altitude species have declined, temperate tropical forests have been reduced and in Mediterranean areas the vegetation maintained by fire has dominated.
"Even with only 2 ° C warming – and potentially only 1.5 ° C -" We can expect sea level rise to become irrepressible for millennia, affecting much of of the world's population, infrastructure and economic activity. "
Yet these significant observed changes are generally underestimated in climate model projections that focus on the short term. Compared to these past observations, climate models seem to underestimate long-term warming and heat amplification in the polar regions
"Climate models seem reliable for small changes, as for scenarios low emissions over short periods. but as the change becomes more important or more persistent, either because of higher emissions, for example a business-as-usual scenario, or because we are interested in the long-term response of a scenario Low emissions, It seems that they underestimate climate change. ", said the co-author of Prof. Katrin Meissner, director of the Center for Climate Change Research at the University of New South Wales
" This research is a powerful call to action. do not worry about the urgency of our emissions, global warming will bring profound changes to our planet and our way of life – not just for this century but beyond. "
