Scientific Colloquium
November 18, 2005



Director, Goddard Institute for Space Studies
New York, New York

James Hansen

Global temperature is now near the peak of the current interglacial period.  Additional global warming of more than 1 degree Celsius could make the earth warmer than it has been in more than a million years.

I will argue that such a global warming level would lead to large changes in sea level, the arctic, and regional climate in general, changes that most people would consider "dangerous".  The earth is now out of energy balance, implying that additional warming of ½ degree Celsius is already "in the pipeline".  All Intergovernmental Panel on Climate Change (IPCC) scenarios for the 21st century yield global warming exceeding 1 degree Celsius.  Greenhouse gas emissions from China and other developing countries are growing rapidly.

Is disastrous global climate change now unavoidable? This is the topic to be discussed.