Why 2 degrees Celsius more warming limit so important

If you read or listen to almost any article about climate change, it’s likely the story refers in some way to the “2 degrees Celsius limit.” The story often mentions greatly increased risks if the climate exceeds 2 degrees C and even “catastrophic” impacts to our world if we warm more than the target.

Recently a series of scientific papers have come out and stated that we have a 5 percent chance of limiting warming to 2 degrees C, and only one chance in a hundred of keeping man-made global warming to 1.5 degrees C, the aspirational goal of the 2015 Paris United Nations Framework Convention on Climate Change conference. Additionally, recent research shows that we may have already locked in 1.5 degrees C of warming even if we magically reduced our carbon footprint to zero today.

And there’s an additional wrinkle: What is the correct baseline we should use? The Intergovernmental Panel on Climate Change (IPCC) frequently references temperature increases relative to the second half of the 19th century, but the Paris Agreement states the temperature increases should be measured from “preindustrial” levels, or before 1850. Scientists have shown such a baseline effectively pushes us another 0.2 degrees C closer to the upper limits.

That’s a lot of numbers and data – so much that it could make even the most climate-literate head spin. How did the climate, and climate policy community, come to agree that 2 degrees C is the safe limit? What does it mean? And if we can’t meet that target, should we even try and limit climate change?

Read the story by David Titley on Yale Climate Connections - “Why 2 degrees Celsius more warming limit so important.”