Most climate scientists would wholeheartedly agree with this statement by the newly elected US president, indeed would have agreed with it twenty years ago. The US National Academy of Sciences first warned of impending global warming in a historic report in 1979, and the head of the NASA climate research division, James Hansen, famously declared, “global warming is here,” in a congressional hearing in 1988. That same year, the World Meteorological Organization founded the Intergovernmental Panel on Climate Change (IPCC).

Since then an incredible wealth of scientific data on global warming has been collected. The history of the Earth's climate has been probed by drilling into the Greenland and Antarctic ice sheets and the sediment layers of the oceans' vast depths. Great advances in computer modeling of our climate have been made. Each year, over 10,000 scientific papers are published with a key word “climate.”

In this book we aim to provide an overview of what we know about the ongoing climate change and its impacts, and what we can do to confront the climate crisis. We base this account closely on the Fourth Assessment Report of the IPCC – a three-year effort of hundreds of scientists from around the world to assess and summarize the scientific literature.