Climate change in context


What follows is a condensed version of a long article about climate change by Andrew Bernstein:

Climate change is real – but the earth has gone through both cyclical and sudden climate change throughout its history.

The earth is about 4 and a half billion years old. So looking at temperature records over the last 150 years or so is a drop in the ocean.

55 million years ago the  earth went through the ‘hot period’ of the Paleocene–Eocene Thermal Maximum. Yet for the last 50 million or so years the world has been cooling.

Even so, temperature has cycled within this time. The Roman Warm Period went from about 250 BCE to 400 CE. During the Medieval Warm Period, from around 900 to 1300, grapes were grown in parts of northern Europe that are too cold to grow grapes today.

Following the Medieval Warm Period was the Little Ice Age, from around 1300-1800. Temperatures in Europe, the North Atlantic, and North America were lower than today, causing migration in some regions, famine and death in others.

Carbon dioxide in the atmosphere is a cause of warming, but only one factor.

Scientists think that at the start of the Industrial Revolution, there were 280 parts per million (ppm) of carbon dioxide in the atmosphere. In 1958 it was 315 ppm, and today it’s just over 400 ppm. But this is only 0.04% of the earth’s atmosphere.

During the Ordovician ice age, about 440 million years ago, there were 10-17 times higher levels of carbon dioxide in the atmosphere than today, yet the earth was in a period of severe glaciation.

Earth’s temperature throughout history seems to have ranged between a global average of 10-23 C (50-73 F). It’s currently around 15 C (59-60 F), near the lower end of the spectrum.

Natural forces are far more powerful than humans. We can’t, for instance, stop hurricanes or smother volcanos. Nature has caused climate changes for millions of years before humans existed and, if history is any guide, will continue to do so.