The Earth’s climate is a complex system that depends on the balance of energy from the sun (the source of most of our sunlight) absorbed by the planet and re-emitted as heat. It also depends on the amount of water vapor in the atmosphere and the extent of polar ice sheets. Any disturbance to this balance can have significant effects on the weather and our daily lives.
Greenhouse gases — like carbon dioxide and methane — trap the sun’s heat in our atmosphere, causing it to warm up. This warming is changing the way our climate works.
There are many things that influence the climate, such as clouds and ice, but greenhouse gases are by far the biggest. Burning fossil fuels releases large amounts of these gases into the atmosphere.
CO2 is made up of three different types of carbon — 12 (representing the oxygen in the air), 13 and 14 (representing the carbon in living systems). Volcanoes produce CO2 with relatively more carbon-13, and it tends to get lighter over time.
When scientists look at historical records of changes in the carbon in our atmosphere, they use something called fingerprinting. It’s a powerful tool for studying the causes of change in our climate. Fingerprinting can tell us which influence triggered the climate record, and it’s also important for determining how quickly and at what rate changes in our planet’s temperature are happening.
Our modern climate is much warmer than it was at any time in the past. This is due to an increase in carbon dioxide, the most important greenhouse gas.
The concentration of carbon in the atmosphere has been rising over the past century. This is caused by the burning of fossil fuels, such as coal and oil.
Historically, atmospheric levels of carbon dioxide have varied over millions of years, depending on volcanic activity and other geologic processes. But when we’ve added a lot of it, as we’ve done over the last several hundred years, CO2 concentrations have been increasing at an alarmingly fast pace.
This rapid rise in carbon dioxide is accelerating the warming we’re seeing. Models of the climate show that if our emissions continue at their current rate, we’re likely to reach a point where global temperatures are as much as 5 degrees Fahrenheit warmer than they were between 1901 and 1960.
The consequences of this warming are being felt across the globe, as we experience increased extremes in temperature and other weather-related impacts. These include increased risks of flooding, storms and droughts.
People in developing nations are at the greatest risk of the impacts of climate change. Their livelihoods are at stake, as are their access to food, water and health care.
It’s also likely that many of the poorest countries will suffer the most, especially those that are already struggling to make ends meet. In the future, there will be a huge difference between those who can afford to avert the impact of climate change and those who cannot.