How Scientists Know Climate Change Is Happening

The Paris climate conference will set nations against each other, and kick off huge arguments over economic policies, green regulations and even personal lifestyle choices. But one thing isn’t up for debate: the evidence for climate change is unequivocal.

We still control the future, however, as the magnitude of shifting weather patterns and the frequency of extreme climate events depends on how much more greenhouse gas we emit. We aren’t facing the end of the world as envisaged by many environmentalists in the late 1980s and early 1990s, but if we do nothing to mitigate climate change then billions of people will suffer.

Causes of climate change

Greenhouse gases absorb and re-emit some of the heat radiation given off by the Earth’s surface and warm the lower atmosphere. The most important greenhouse gas is water vapor, followed by carbon dioxide and methane, and without their warming presence in the atmosphere the Earth’s average surface temperature would be approximately -20°C. While many of these gases occur naturally in the atmosphere, humans are responsible for increasing their concentration through burning fossil fuels, deforestation and other land use changes. Records of air bubbles in ancient Antarctic ice show us that carbon dioxide and other greenhouse gases are now at their highest concentrations for more than 800,000 years.

Evidence for climate change

The Intergovernmental Panel on Climate Change (IPCC) presents six main lines of evidence for climate change.

  1. We have tracked the unprecedented recent increase in the amount of atmospheric carbon dioxide and other greenhouse gases since the beginning of the industrial revolution.

  2. We know from laboratory and atmospheric measurements that such greenhouse gases do indeed absorb heat when they are present in the atmosphere.

  3. We have tracked significant increase in global temperatures of at least 0.85°C and a sea level rise of 20cm —> Read More