Global warming attribution studies consistently find humans are responsible for all global warming over the past six decades.
Severe Flooding, Against a Background of Wind Turbines: November 2012, Tyringham, Bucks. (Image: T. Larkum)
A new study published in Climate Dynamics has found that humans are responsible for virtually all of the observed global warming since the mid-20th century. It’s not a novel result – in fact, most global warming attribution studies have arrived at the same general result – but this study uses a new approach.
Studies attempting to figure out the global warming contributions of various human and natural sources usually use a statistical approach known as ‘linear regression’. This approach assumes we know the pattern of warming that each source (forcing) will cause, but we don’t know how big the resulting warming will be. For example, we know that greenhouse gases cause more warming over land than water, the most in the Arctic, and more warming in response to rising atmospheric carbon dioxide levels.
As an example of this approach, this animated graphic shows what happens when a 2011 study by Foster & Rahmstorf removed the known natural influences from the observed global surface temperature record, leaving behind the human-caused global warming signal.
We have an idea how much warming greenhouse gases will cause, but the range is fairly large (1.5 to 4.5°C in response to a doubling of atmospheric carbon dioxide). So, the standard approach uses the known patterns from each forcing (greenhouse gases, other human pollutants, the sun, volcanoes, etc.), and without assuming the effectiveness of each, statistically determines how much each pattern has contributed to the observed temperature changes.
Read more: The Guardian