Scientists have developed an understanding of the earth’s climate system through years of observations. We now know that global warming is the result of greenhouse gas emissions caused by human activity.
Since the late 19th century, the global average temperature has risen by about 1°C and the global sea level has risen by about 20cm. The rising temperature is leading to wider changes to our weather. At the same time, increased CO2 levels are causing the world’s oceans to become more acidic.
Many impacts of climate change are already being detected, including:
- warming of the troposphere (the lower part of the atmosphere)
- acidification of the oceans
- rising sea levels
- declining glaciers and sea ice
- slowing of increases to crop productivity
There is no clear threshold where climate change moves from safe to dangerous. We can expect some disruptions and irreversible losses of natural habitats and resources, even with a 2°C temperature rise.
However, with rapid global action to cut greenhouse gas emissions, we can still reduce the likelihood of global temperatures increasing by 2°C. On the other hand, if we take no action, global temperatures could increase by 7°C or more.
That is why it is sensible to take action now to insure against the risks of dangerous climate change.
Read the latest evidence about how and why our global climate is changing from some of the world’s leading science organisations:
- The Intergovernmental Panel on Climate Change provides the most comprehensive summaries of the latest research on climate science and the impacts of climate change.
- The UK Royal Society and the US National Academy of Sciences are fellowships of the world’s most eminent scientists. Together they have published a joint statement on the science of climate change.
- The Geological Society has published a document setting the evidence for (and risks of) climate change from a geological perspective.
- The American Institute of Physics hosts a detailed history of the discovery of global warming.
What is causing climate change?
Geological records stretching back millions of years indicate a number of large variations in Earth’s climate. However, comprehensive assessment by scientists shows that it is extremely likely that human activity has been the dominant cause of warming since the mid-20th Century.
Measuring a warming world
Climate change is most commonly measured using the average surface temperature of the planet. Estimates from the UK Met Office, NASA, US National Climatic Data Centre and Berkeley Earth all show a rising trend in average global temperature over the last century.