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It starts as a reasonable question: If the Earth’s climate changed before humans existed, how can we be sure that the current changes are caused by us and not by nature?
To answer that question, we need to understand the causes of natural change in the past. Fortunately, science has successfully dealt with the causes of Earth’s natural climate change that go back hundreds of millions of years. Some were cyclical. Others were gradual changes or sudden events, but none explain today’s changing climate.
claim of zombies
With energy policy and elections in the news, claims by some politicians that climate change is a natural phenomenon are resurfacing from a swamp of disinformation. So I asked some scientists a very unscientific question: If they had a dollar every time they heard it, what would they buy?
Matthew Owens, a professor at the University of Reading, said, “It’s a heat pump in my house. It’s a time machine to persuade policymakers decades ago to deal with climate change,” said Michael Mann, a professor at the University of Pennsylvania. Professor Anja Schmidt of the German Aerospace Center and the Universities of Munich and Cambridge made a film to explain that “the volcano is not to blame”, while Professor Tim Renton of the University of Exeter “should not teach such things in schools”. I appealed to the government.”
“I love cycling so much that I will probably buy another bike,” Professor Michel Crucifix of the University of Louvain, Belgium, told me. His Jeremy Caves Rugenstein professor at Colorado State University said:
Fortunately, these scientists had much more to say than just the natural forces of climate change and their role in today’s global warming.
it’s not the sun
Since the sun is the source of energy on the earth’s surface, it is not surprising that fluctuations in solar activity can lead to climate change. However, solar activity has declined over the past few decades with global warming, so the relevance is irrelevant. Solar energy is huge, but variation Small.
“This has long been called the ‘constant’ of the sun. very A sensitive instrument for identifying changes in the sun’s energy output,” Owens said. In an 11-year sunspot cycle, the solar energy reaching the top of the atmosphere fluctuates by about 0.15%, but it increases or decreases with each cycle, so it can’t drive climate trends like ours.
NASA-JPL/Caltech
In addition to these 11-year cycles, the Sun also goes through “Great Solar Minimums” and “Solar Maximums” of activity that last for decades. One of them, called the “Maunder Minimum”, was once thought to be responsible for his cold period around 1300-1850 called the Little Ice Age. ‘ But ‘that doesn’t add,’ Owens told me. “Temperatures start to drop long before the Maunder Minimum occurs.”
The Maunder Minimum may have contributed a small percentage to the cooling of the Little Ice Age, and evidence since then has shown that it was the result of volcanic eruptions and human-induced land-use change.
The Sun also regulates the dose of cosmic rays it gives to our atmosphere. These are mostly protons originating in space, such as from supernovae, and in the late 1990s there was the idea that they could affect climate by seeding cloud formation. But Owens says the data show no correlation, and experiments using the CERN particle accelerator show weak seeding of clouds by cosmic rays. “The droplet growth rate is too small to really do anything in the atmosphere,” Owens said, so it can’t explain the Little Ice Age or modern climate change.
Owens is overwhelmed by the Sun’s current activity. He said.
