Climate Lab BookFebruary 25, 2022
Ed Hawkins ✨
Climate Change 2021 – the physical science basis
SNIPPET:
This blog post is a short summary of key points that are of current relevance to society from the physical science of climate change. It is based on the headline statements of a report
published in 2021 by the Intergovernmental Panel on Climate Change (IPCC). The IPCC is a United Nations body responsible for providing impartial assessments of climate science. Its reports inform international negotiations on tackling climate change.
Written by Jonathan Gregory, Matt Palmer and Ed Hawkins
How and why has the climate changed?Widespread and rapid changes have taken place in the atmosphere, in the ocean and on land. There is no doubt that the climate has warmed because human activities have increased the amounts of greenhouse gases in the atmosphere, especially carbon dioxide (CO2) and methane (CH4).
Greenhouse gases warm the climate by making it harder for the atmosphere to radiate heat into the surrounding universe (space). They insulate the atmosphere against losing heat, rather like making it warmer inside a house by insulating the roof. The physics of this greenhouse effect has been understood for more than a century.
The largest human-caused effect on climate is due to the build-up of CO2, mostly from
burning fossil fuels (coal, oil and gas). The size and speed of recent changes in many aspects of the climate system
exceed any seen for
hundreds or thousands of years (Figure 1).
Figure 1: Changes since the year 1 (of the Common Era, or AD) in the amount of CO2 in the atmosphere and in the global-average surface temperature. The industrial revolution and the burning of fossil fuels to produce energy began with the invention of the steam engine.The warming causes changes in many other aspects of climate. For example,
many extreme weather and climate events in every region across the globe have
already become more severe or more frequent due to human-caused climate change (Figure 2).
Figure 2: This diagram depicts how much more often extremely high temperatures occur as the climate gets warmer. As an example, it considers the temperature which was reached only once in 50 years on average at any given place in the climate before the industrial revolution. This extreme happens more frequently in today’s climate, and will become still more common in warmer climates.What climate change will happen in future?Improved scientific knowledge has narrowed the range of warming expected as a result of increasing the amount of CO2 in the atmosphere.
Full article:
https://www.climate-lab-book.ac.uk/2022/climate-change-2021/