How the Climate Works

The Earth’s climate has warmed and cooled many times over millions of years.

Most of these changes took place over many thousands of years in response to natural processes.

Past changes in the global climate can be explained by a range of factors, which scientists call ‘forcings’.

Current changes in the global climate are caused by rising levels of greenhouse gases such as methane and carbon dioxide in the atmosphere.

A HISTORY OF CHANGE

Antarctic climate through time

Antarctica is no stranger to a changing climate. In fact, 90 million years ago there was no ice in the polar regions at all. Sea levels were hundreds of feet higher than today, and Antarctica was covered in swampy rainforest where tree ferns and conifers flourished and dinosaurs roamed.

Image credit: James McKay/ Alfred Wegener Institute; Creative Commons license CC-BY 4.0

Our civilization has matured and thrived through a period of remarkable climatic stability.

Muir Glacier, Alaska. Photographed by William Osgood in 1941 (left) and Bruce Molnia in 2004 (right).

Images courtesy of NSIDC Glacier Photograph Collection.

When we burn fossil fuels such as coal, oil and gas we release carbon dioxide, which acts like a greenhouse around the planet, trapping warm air and heating it up. Scientists first recognized this in the late 1800s.

By the 20th century this effect was well underway, and in 1988 a NASA scientist named James Hansen testified before the U.S Congress, saying that the climate was warming because of greenhouse gasses released by human activity. That same year, the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP) established the Intergovernmental Panel on Climate Change (IPCC), bringing together experts from around the world to better understand the climate, and how and why it was changing.

Technicians working on an Antarctic ice core. Photo credit: Marlo Garnsworthy / IODP

Over the past three decades, our understanding of the climate has grown significantly. Thanks to new technologies such as satellites, ground-penetrating radar and the analysis of polar ice cores, researchers have been able piece together the climate of the past, and see how it has changed through time. They are also able to gather important data on the climate today, which helps them predict how it may change in the future.

Researchers found that by releasing vast volumes of carbon dioxide and methane into the atmosphere, humans are triggering rapid changes in our climate unlike anything seen in at least 800,000 years.

In 2014, as part of the Intergovernmental Panel on Climate Change (IPCC) under the auspices of the United Nations, a group of 1,300 independent scientific experts from countries all over the world released a report on the state of the climate.

According to the IPCC, “warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia.”