The extent of the human contribution to modern global warming is a hotly debated topic in political circles, particularly in the US. During a recent congressional hearing, Rick Perry, the US energy secretary, remarked that “to stand up and say that 100% of global warming is because of human activity, I think on its face, is just indefensible”.
However, the science on the human contribution to modern warming is quite clear. Humans emissions and activities have caused around 100% of the warming observed since 1950, according to the Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report.
Read here for a Carbon Brief analysis of how each of the major factors affecting the Earth’s climate would influence temperatures in isolation – and how their combined effects almost perfectly predict 13
Carbon Brief’s analysis finds that:
- Since 1850, almost all the long‐term warming can be explained by greenhouse gas emissions and other human activities.
- If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred. They are offset by cooling from human‐produced atmospheric aerosols.
- Aerosols are projected to decline significantly by 2100, bringing total warming from all factors closer to warming from greenhouse gases alone.
- Natural variability in the Earth’s climate is unlikely to play a major role in long‐term warming.
Read more here.
First published by Carbon Brief, 13 December 2017.