Climate Change 101 - Part 1

Is the climate changing? Is it due to human activity? What should we do about it? These are questions you might have on your mind from hearing about climate change from the media and politicians. While climate change seems like a popular topic right now, most of what you hear about it on a day to day basis is more about the adaptation and mitigation strategies than the science of why and how it is actually happening.

Although the earth’s climate has been constantly changing and evolving since the earth began, the current rate of change is unusual. Global temperatures have increased more rapidly since the Industrial Revolution than during the past thousand years, according to data from tree rings and boreholes. The graph below shows how temperatures have changed since 800 AD according to a handful of data sources. (For more information on this graph, see the IPCC Fourth Assessment Working Group 1 report, Chapter 6 – http://www.ipcc.ch/ipccreports/ar4-wg1.htm). The rapid rate of change, along with its connection to human activities, is why climate change is such an important issue.



Although climate change has been politicized, it’s really a scientific issue. There is a scientific relationship between atmospheric carbon dioxide and global temperatures. Like climate change, this link is nothing new. For example, during the Cretaceous period (145 to 65 million years ago), evidence from fossils suggests that atmospheric carbon dioxide concentrations were much higher than they are today and that global temperatures were several degrees warmer. Almost the entire earth had a tropical climate. The difference between the current warming and the Cretaceous warming is the cause of high CO2. While past causes of high CO2 were natural, today’s primary cause is not. In the past, atmospheric carbon dioxide was high due to increased volcanism and decreased weathering. Today, carbon dioxide is on the rise due to the burning of fossil fuels.

Although how we should respond to climate change is highly debatable, the reasons for the rising temperatures are not. They come down to the physics of radiation and the chemistry of molecular structure. They are topics you probably covered in your middle school science classes. It’s time for a little refresher.