Climate models may not be presenting a correct picture of the extent of global warming, reveals a new international study by researchers from 17 countries worldwide. As the world works towards the 2°C target, study findings released recently indicate even this may not be enough to check future global warming.
The international researchers studied observational evidence from three warm periods over the past 3.5 million years.
According to the study, future global warming may eventually be twice as warm as projected by climate models. This may cause sea levels to rise six metres or more, large areas of the polar ice caps to collapse, Sahara Desert to become green, and the edges of tropical forests to turn into fire dominated savanna.
Based on the study of past documented warming periods, there are a number of amplifying mechanisms that are not reflected in climate model projections. This means the climate models do not represent a true picture of the extent of global warming today.
The researchers studied the Holocene thermal maximum (5000-9000 years ago), the last interglacial (129,000-116,000 years ago) and the mid-Pliocene warm period (3.3-3 million years ago).
While global warming in the first two periods was caused by predictable changes in the Earth's orbit, the mid-Pliocene event was the result of atmospheric carbon dioxide concentrations of 350-450ppm, similar to current day figures.
These conditions seriously impacted the Earth with consequences including substantial retreats of the Antarctic and Greenland ice sheets, sea levels rising by at least six metres; marine plankton ranges shifting to reorganise the entire marine ecosystem; and the greening of the Sahara among many more.
The increase in carbon emissions is dramatically speeding up the pace of global warming today; even if these emissions stopped completely, it would still take centuries to recover.
Current climate models seem to underestimate long term warming and its consequences.