Contents

Title Page and Notice		i
National Academies Statement		iii
Committee		v
Foreword		vii
Acknowledgments		ix
SUMMARY		1
1	CLIMATE, CLIMATE FORCINGS, CLIMATE SENSITIVITY, AND TRANSIENT CLIMATE CHANGE	6
	Climate	6
	Climate Forcings	6
	Climate Sensitivity	6
	Transient Climate Change	7
2	NATURAL CLIMATIC VARIATIONS	8
3	HUMAN CAUSED FORCINGS	9
	Greenhouse Gases	9
	Aerosols	12
	Climate Forcings in the Industrial Era	12
4	CLIMATE SYSTEM MODELS	15
5	OBSERVED CLIMATE CHANGE DURING THE INDUSTRIAL ERA	16
	The Occurrence of Climate Change	16
	The Effect of Human Activities	17
6	FUTURE CLIMATE CHANGE	18
	Estimating Future Climate Change	18
7	ASSESSING PROGRESS IN CLIMATE SCIENCE	22
	Intergovernmental Panel on Climate Change	22
	Research Priorities	23
APPENDIXES
A	Letter from the White House	27
B	Biographical Sketches of Committee Members and Staff	28