As the Copenhagen Climate Conference is taking place, it is appropriate to clarify once again what is more or less accurately known about the climate of our planet and about climate change.
Obviously, a brief post can not substitute for detailed studies of professionals in a variety of scientific disciplines – climatology, atmospheric physics, chemistry, geology, astronomy, and economics. However, a short post can summarize basic theses on the main trends in climate evolution, on its forecasts, and on its actual and projected effects.
1. The Earth’s climate is constantly changing. The climate was changing in the past, is changing now and, obviously, will be changing in the future – as long as our planet exists.
2. Climatic changes are largely cyclical in nature. There are various time horizons of climatic cycles – from the annual cycle known to everyone to cycles of 65–70 years, of 1,300 years, or of 100,000 years (the so called Milankovitch cycles).
3. There is no fundamental disagreement among scientists, public figures and governments about the fact that the climate is changing. There is a broad consensus that climate changes occur constantly. The myth, created by climate alarmists, that their opponents deny climate change is sheer propaganda.
4. Current debate among climatologists, economists and public figures is not about the fact of climate change, but about other issues. In particular, disagreements exist on:
— Comparative levels of modern day temperatures (relative to the historically observed),
— The direction of climate change depending on the length of record,
— The extent of climate change,
— The rate of climate change,
— Causes of climate change,
— Forecasts of climate change,
— Consequences of climate change,
— The optimal strategy for human beings to respond to climate change.
5. Unbiased answers to many of these issues are critically dependent on a chosen time horizon – whether it is 10 years, or 30 years, or 70 years, or 1000 years, or 10,000 years, or hundreds of thousands or millions of years. Depending on the time horizon, the answers to many of these questions may be different, even opposite.