One of the most hotly debated numbers in climate science is how warm our planet will become given various green house gas levels. The degree to which warming will occur depends on the amount of emissions, which make these calculations crucial for global policy making to curb global warming. But a UW study shows that two leading methods for calculating how hot the planet will get are not as far apart as they have appeared.
The new study, published April 17 in Nature Climate Change, focuses on the lag time in Earth’s response. According to most models of climate change, during the early stages of global warming the sensitivity to greenhouse gas emissions is relatively small. As the ocean catches up and feedbacks kick in, however, the sensitivity increases and the warming rate speeds up. The new study shows that when this difference is factored in, the observations and climate models are in agreement, with recent observations supporting a previously accepted long-term climate sensitivity of about 2.9 degrees Celsius.
“The key is that you have to compare the models to the observations in a consistent way,” said author Kyle Armour, a UW assistant professor of oceanography and atmospheric sciences. “This apples-to-apples approach — where you factor in how long the planet has been adjusting to a change in its atmosphere — shows that climate sensitivity in the models is actually in line with what has been seen in the recent observations.”
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