Human-made climate change started twice as long ago as we thought

Man-made climate change began 180 years ago – much earlier than previously assumed, according to a new study by an international team of researchers.

New research found that human activity has been causing global warming for almost two centuries, proving human-induced climate change is not just a 20th century phenomenon.

The research, published in Nature, involved 25 scientists from across Australia, the United States, Europe and Asia, working together as part of the international Past Global Changes 2000 year (PAGES 2K) Consortium.

The research was led by Associate Professor Nerilie Abram from the Australian National University and co-authored by Australian Antarctic Division and Antarctic Climate and Ecosystems Cooperative Research Centre glaciologist Dr Mark Curran.

Lead researcher Associate Professor Nerilie Abram from The Australian National University (ANU) said the study found warming began during the early stages of the Industrial Revolution and is first detectable in the Arctic and tropical oceans around the 1830s, much earlier than scientists had expected.

It was an extraordinary finding,” said Associate Professor Abram, from the ANU Research School of Earth Sciences and ARC Centre of Excellence for Climate System Science.

“It was one of those moments where science really surprised us. But the results were clear. The climate warming we are witnessing today started about 180 years ago.”

Associate Professor Abram said anthropogenic climate change was generally talked about as a 20th century phenomenon because direct measurements of climate are rare before the 1900s.

However, the team studied detailed reconstructions of climate spanning the past 500 years to identify when the current sustained warming trend really began.

Program Leader with the Australian Antarctic Division, Dr Tas van Ommen, said significant human-induced warming was previously thought to have been a 20th century phenomenon.

“The new climate data, stretching back five centuries, allows us to see the warming in its earliest stages, progressing across the globe,” Dr van Ommen said.

“It shows the Earth’s climate is sensitive to even small changes in greenhouse gas levels providing a valuable context for modelling future climate.”

The research found that warming in parts of the Southern Hemisphere was delayed up to 50 years, and that the Antarctic continent is yet to show significant overall warming.

“Antarctica has been buffered from major continent-wide changes due to its thermal isolation, with the Southern Ocean muting warming in the Southern Hemisphere and Antarctica.

“The westerly winds that circle Antarctica reduce warm air reaching the continent, ozone depletion and rising greenhouse gases have acted to make this wind barrier stronger,” Dr van Ommen said.

The westerly winds have also had complicated influences on the ocean around Antarctica.