Global Temperatures are Expected to Rise by 4°C by 2100
According to a Dec. 31 news release from the University of New South Wales, global temperatures are expected to rise by 4°C by 2100 if carbon dioxide emissions are not scaled back. Researchers also say that the continued increase in global average temperatures will result in an additional 4°c by 2200.
The findings are published in a recent article in the journal Nature, and may explain one of the great unknowns of climate sensitivity: the role of cloud formation and whether this will have a negative or positive effect on overall global climate change.
“Our research has shown climate models indicating a low temperature response to a doubling of carbon dioxide from preindustrial times are not reproducing the correct processes that lead to cloud formation,” said Steven Sherwood, a professor from the University of New South Wales’ Centre of Excellence for Climate System Science. “When the processes are correct in the climate models the level of climate sensitivity is far higher. Previously, estimates of the sensitivity of global temperature to a doubling of carbon dioxide ranged from 1.5°C to 5°C. This new research takes away the lower end of climate sensitivity estimates, meaning that global average temperatures will increase by 3°C to 5°C with a doubling of carbon dioxide.”
The key to this narrower – albeit much higher – estimate is found in the real observations around the role of water vapor in cloud formation per Science Recorder.
Observations show when water vapor is taken up by the atmosphere due to evaporation, the updrafts can either rise to from 15km to just a few kilometers to form clouds that produce heavy rains before falling back to the surface without forming rain clouds.
The researchers uncovered that climate models that show a low global temperature response to carbon dioxide do not include enough of this lower-level water vapor process. In its place, they simulate all updrafts rising to 15km and forming clouds.
The result is such that, when water vapor processes are correctly represented, the sensitivity of the climate to a doubling of carbon dioxide means Global Temperatures are expected to rise by at least 4°C by 2100.