Man-made climate change began earlier than we once thought

Most people, when asked about the impact of mankind on climate change, would assume that this is a relatively recent phenomenon caused by the steady increase in recent decades of carbon dioxide emissions due to such things as air travel and motor vehicles, as well as heavy industry.

However, the evidence suggests that human-induced climate change began as long ago as the early decades of the 19^th century, not long after the Industrial Revolution led to fossil fuels (notably coal) being burned in large quantities.

Ocean evidence

The evidence comes from data gathered by examining ocean corals and other marine organisms. This source of data is vital because the oceans have absorbed more than 90% of the warming caused by climate change, and corals can provide temperature data going back at least 500 years.

Effect of volcanoes

Evidence of global warming would have difficult to spot in earlier decades if only land-based measurements were relied upon. This is in part because the early 19^th century experienced several massive volcanic eruptions, most notably that of Mount Tambora in 1815, that had an overall cooling effect on global temperatures and masked any rises due to other causes. Any mid-century rise would be seen as a natural recovery from the earlier cooling as the atmospheric dust clouds dispersed.

However, computer simulations that remove the effect of volcanic eruptions from the data show very clearly that there was a notable rise in temperatures from the 1830s that can only have industrial emissions as the cause.

Steady rise

These models are in line with the evidence from ocean corals and show very clearly that climate change from human causes dates from the mid-19^th century and has been increasing ever since.

© John Welford