Climate change writer mixing apples, oranges

A recent letter pointed to the retreat of ice sheets and glaciers during the past 14,000 years as evidence that climate has been changing for a long time and without humans causing it. This fact is well-known to geoscientists and climate scientists and has been for at least a century. In fact, the science of climate change originated as enquiry into the causes and effects of natural variability in Earth’s climate.

The author of that letter was mixing apples and oranges. There is no debate amongst the vast majority of earth scientists that climate varies naturally, but added to this now are the effects of human activity and the burning of fossil fuels. Scientists use a range of techniques and data sources to study climate. Rather than just pointing to one or two pieces of evidence, as the writer did, and those taken out of context, I urge interested people to try to look at a more complete picture. Most people will not be able to read the vast scientific literature on the topic, but the Intergovernmental Panel on Climate Change has compiled and boiled down much of the science into digestible summaries that are posted online at

Carbon dioxide in the atmosphere has dramatically increased in concert with our use of fossil fuels, and average global temperatures are rapidly increasing as well. These are facts, not speculation. Models, which do have uncertainties, are used to make predictions and most of these are being borne out as time progresses. One can criticize the cost of so-called “half-baked policies” aimed at reducing greenhouse gases, but an honest debate must also address the costs of not doing so, including mitigation of increased flooding of coastal areas and increasing weather extremes.

Greg Valentine