The world is staring down the barrel of climate change that is faster than at any time in the last 50 million years, according to Chris Field, a senior fellow at the Stanford Woods Institute.

At this year’s American Association for the Advancement of Science (AAAS) Annual Meeting in Chicago on Feb. 14, Field described what analysis of 27 climate models revealed about the pace of climate change and what risks and emerging challenges we should expect.

“The rates of warming we’re predicting by the end of this century are dramatically higher than we’ve seen for the past 50 million years,” Field said in his talk based on a paper he co-authored with Stanford Woods Institute Senior Fellow Noah Diffenbaugh (Earth Sciences),

Field is co-chair of the U.N. Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Working Group II, which will release its report on climate impacts, adaptation and vulnerability March 31. He pointed out that the rate of climate change predicted by 2100 outpaces the most significant known climate changes in Earth’s history, such as transitions to and from ice ages.

If unchecked, the mean yearly rate of 21st century global warming could exceed 3.6 degrees Fahrenheit (2 degrees Celsius) over most terrestrial regions during the period spanning 2046 to 2065, and then increase to 7.2 degrees Fahrenheit (4 degrees Celsius) during the period spanning 2081 to 2100, according to Field. Field observed that these anticipated temperature increases could, by the end of the century, bring to Chicago heat patterns like those in Miami or Houston.

By comparison, the biggest global climate change known to scientists – an ice age cooling 55 million years ago – saw temperatures change only a few hundredths of a degree per decade.

Carbon dioxide concentrations over the last 800,000 years “didn't even approach the levels we’re currently at,” Field said. Over the past 22 million years, there have only been three or four periods when carbon dioxide levels approached current concentrations, and there is no evidence that carbon dioxide levels ever reached the levels that are expected by the end of this century, according to Field.

Among other challenges, this pattern will likely strain efforts to increase crop yields and force animals and plants to find new habitats, Field said. “We know very little about the ability of plants, animals and humans to adapt to these rates of change.”

Instead of seeing climate models as definitive predictions, decision-makers should see them as possible scenarios that can help inform adaptation and mitigation policy, Field said. “We should be translating those projections through the lens of managing risks.” Waiting to act will only make the problem harder to solve, more expensive and more likely to intensify, Field added

Field is the Melvin and Joan Lane Professor for Interdisciplinary Environmental Studies at Stanford, a senior fellow at the Precourt Institute for Energy and director of the Carnegie Institution’s Department of Global Ecology.