Earth can be twice as hot as expected

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Geneva

The Earth can be twice as much hot than projected by climate models, even if the world reaches the goal of limiting global warming to less than two degrees Celsius, a study found.
The study, published in the journal Nature Geoscience, has shown that sea levels can rise six meters or more even if the Paris climate goals are met.
The results are based on observational evidence of three warm periods over the past 3.5 million years when the world was 0.5 to 2 degrees Celsius warmer than the pre-industrial temperatures of the 19th century.
The research also revealed how large areas of ice caps could collapse and significant changes in ecosystems could see the Sahara Desert become green and the edges of the rainforests turn into fire-dominated savannahs.
"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," said Hubertus Fischer of the 39, University of Bern, Switzerland.
"This suggests that the carbon budget to avoid 2 degrees Celsius of global warming could be much smaller than expected, leaving a very small margin of error to reach the Paris targets," Fischer said.
To obtain their results, the researchers examined three of the best-documented warm periods, the Holocene thermal maximum (5,000-9,000 years), the last interglacial (129,000-116,000 years), and the warm period middle of the Pliocene (3.3- 3 million years ago).
The warming of the first two periods was 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.
By combining a wide range of measurements from ice cores, sediment layers, fossil recordings, atomic isotope dating and a host of other established paleoclimatic methods, researchers have reconstructed the impact of these climate changes.
In combination, these periods clearly show how a warmer Earth would appear once the climate stabilized. By contrast, today, our planet is warming much faster than any of these times, as human-caused carbon dioxide emissions continue to grow.
Even if our emissions ceased today, it would take centuries or millennia to reach equilibrium.
The changes in the Earth under these past conditions were profound: the Antarctic and Greenland ice sheets have considerably retreated and, as a result, the sea level has risen 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 degrees Celsius warming – and potentially only 1.5 degrees Celsius – the significant impacts on the Earth's system are profound," said Alan Mix of Oregon State University in the United States.
"We can expect sea level rise to become irrepressible for millennia, affecting much of the world's population, infrastructure, and economic activity," said Mr. Mix. . PTI