How Greenhouse Gases Influence Climate

The latest round of UN climate change talks is currently underway in Lima, Peru. Representatives from nearly 190 countries are meeting to discuss ways to reduce greenhouse gas emissions, the main driver of global warming.

Earth’s atmosphere is made up of a variety of gases, mostly nitrogen and oxygen by volume. The greenhouse gases, including water vapor, carbon dioxide, and methane, represent a smaller percentage, but are also a natural part of the mix. Acting like the windowpanes of a traditional glass greenhouse, these gases allow the sun’s energy (shortwave radiation) to pass through the atmosphere during the day and heat the Earth’s surface. At night, the greenhouse gases trap some of the heat (long-wave radiation) that the surface emits as it cools.  In essence, greenhouse gases function like a blanket that help keep the planet warm. Without them, the average surface temperature of the Earth would be 0°F – a temperature at which all the water on the planet would be frozen and life as we know it would not exist. Having too many greenhouse gases is also a problem – one that we are currently facing.

Simply put, more greenhouse gases in the atmosphere trap more heat and increase the planet’s average temperature. During the last century, according to the IPCC, Earth’s mean temperature rose 1.5°F.  As temperatures continue to rise, long established weather patterns and storm tracks are shifting. Different regions, in turn, are being affected in different ways. Some areas are getting wetter, while others are getting dryer, and coastal communities are feeling the impacts of rising sea levels.

Scientists say that while some greenhouse gases come from natural sources like volcanic eruptions, the vast majority entering our atmosphere today come from human activities that burn fossil fuels. Before the industrial revolution in the late 1700’s, atmospheric carbon dioxide levels were 280 parts-per-million (ppm). This year, it passed 400ppm for the first time in human history. In addition, according to NOAA, 2014 is on track to be the planet’s warmest year on record.

Any agreements reached in Lima on reducing greenhouse gas emissions will be used as the framework for a binding global treaty at the UN Climate Conference in Paris next year.