John Cook explains the warming which started in the mid-1970s.
What happened since 1975?
Clearly since about 1975, global surface temperatures have trended rapidly upwards (at a rate of nearly 0.2°C per decade). So what caused the mid-century cooling to end?
The main cause of the sudden shift in global temperature trends was the passage of Clean Air Acts by various countries in response to air pollution and acid rain.
Why did climate cool in the mid-20th Century?
The IPCC says :
Science 26 January 2001:
Vol. 291 no. 5504 p. 566
DOI: 10.1126/science.291.5504.566A
NEWS OF THE WEEK
CLIMATE CHANGE
It’s Official: Humans Are Behind Most of Global Warming
Richard A. Kerr
The United Nations-sponsored Intergovernmental Panel on Climate Change officially declared early this week that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.” The panel was vaguer than ever, though, about how bad things could get by the end of the century. At a minimum, the world will warm more than twice as much in the coming century as it did in the past one, the panel concluded, but it could warm 10 times as much.
It’s Official: Humans Are Behind Most of Global Warming
The logic here is very straightforward. Temperatures have risen over the last 50 years because the US, UK and New Zealand passed Clean Air Acts. But the rise which was due to our cleaning the air was actually due to our dirtying the air with invisible CO2. The US, UK and New Zealand make up 7% of the Earth’s area, and of course control the Earth’s climate.
No doubt the PDO shift in 1976 had nothing to do with the warming, and no doubt these climate experts have the combined IQ of a turnip.
