Chapter 14: Climate change The earth’s changing climate The earth’s changing climate Possible causes of climatic change Possible causes of climatic change Global warming Global warming

The Earth’s changing climate

Determining past climates fossil evidence fossil evidence sediment cores sediment cores ice cores ice cores oxygen isotope ratios oxygen isotope ratios dendrochronology dendrochronology As the global warming debate has intensified in recent years, many methods of reconstructing past climates have undergone close scrutiny. As the global warming debate has intensified in recent years, many methods of reconstructing past climates have undergone close scrutiny.

Climate through the ages ice age ice age interglacials interglacials Younger-Dryas Younger-Dryas 20,000 years ago the sea level was so low that the English Channel didn’t even exist. 20,000 years ago the sea level was so low that the English Channel didn’t even exist.

Climate during the past 1000 years Little ice age Little ice age The graph of temperatures during the past 1000 years is known as the “Hockey Stick” graph The graph of temperatures during the past 1000 years is known as the “Hockey Stick” graph

Temperature trend during the past 100-plus years sources of temperature measurements sources of temperature measurements global warming global warming The global warming of the past 100 years has not been constant. The global warming of the past 100 years has not been constant.

Possible causes of climate change

External causes of climate change changes in incoming solar radiation changes in incoming solar radiation changes in the composition of the atmosphere changes in the composition of the atmosphere changes in the earth’s surface changes in the earth’s surface Emissions of CO 2 and other greenhouse gases are by no means the only way to change the climate Emissions of CO 2 and other greenhouse gases are by no means the only way to change the climate

Climate change and feedback mechanisms positive feedback mechanisms positive feedback mechanisms negative feedback mechanisms negative feedback mechanisms water vapor-greenhouse feedback water vapor-greenhouse feedback snow-albedo feedback snow-albedo feedback Feedbacks cause climate changes to be either amplified or reduced. Feedbacks cause climate changes to be either amplified or reduced.

Climate change, plate tectonics, and mountain- building theory of plate tectonics theory of plate tectonics

Climate change and variations in the earth’s orbit Milankovitch theory: - eccentricity - obliquity - precession Milankovitch theory: - eccentricity - obliquity - precession

Climate change and atmospheric particles sulfate aerosols sulfate aerosols volcanic aerosols volcanic aerosols Sulfate aerosols are thought to cool the climate and therefore counteract global warming to some extent. Sulfate aerosols are thought to cool the climate and therefore counteract global warming to some extent.

Climate change and variations in solar output sunspots sunspots Maunder minimum Maunder minimum

Global warming

The recent warming Radiative forcing agents Radiative forcing agents climate models and recent temperature trends climate models and recent temperature trends Climate models are under constant development and improvement. Climate models are under constant development and improvement.

Future warming - projections, questions and uncertainties Questions and uncertainties about greenhouse gases Questions and uncertainties about greenhouse gases uncertain effect of clouds uncertain effect of clouds

Possible consequences of global warming projected temperatures projected temperatures What will a warmer world be like? What will a warmer world be like? possible effects on the jet stream and global circulation patterns possible effects on the jet stream and global circulation patterns Some scientists believe global warming creates more good than harm - more carbon dioxide is good for plant life, and warmer temperatures will allow agriculture in areas that currently are too cold to support it. Some scientists believe global warming creates more good than harm - more carbon dioxide is good for plant life, and warmer temperatures will allow agriculture in areas that currently are too cold to support it.

Global warming and human impact on the earth’s surface desertification desertification deforestation deforestation

Curbing global warming Kyoto Protocol Kyoto Protocol