Climate Change I: Lines of Evidence
Climate Change I: Lines of Evidence
Anthropogenic Greenhouse Gas Emissions
AR4 WGIII TS
Global totals, anthropogenic emissions, for year 2000
USA – CO2 emissions from fossil fuel combustion (2005)
US EPA
Decreasing 13C strongly suggests that the source of atmospheric CO2 is fossil carbon
Line of evidence #1: Physics
Line of evidence #1: Physics with numbers
Line of evidence #2: Paleoclimate
Where do these data come from??
Paleoclimate to 650,000 years
European Project for Ice Coring in Antarctica
Paleoclimate to 5 million years
Paleoclimate to 65 million years
Line of evidence #3: Observations
Global average observed warming is 0.7 °C (1.3 °F) since 1860.
IPCC, 2007
Line of evidence #3: Observations • Eleven of the twelve years from 1995-2006 were the warmest on record • Average ocean temperature has increased to depths of at least 3 km • Arctic temperatures have increased at twice the global average • Since 1978, average arctic sea ice extent has shrunk by 2.7% per decade • Area covered by permafrost in the Northern Hemisphere has decreased by 7% since 1900 • More intense and longer drought have occurred since the 1970s, particularly in the tropics
IPCC, 2007
Other changes consistent with increasing temperature Increasing global ocean temperatures
Linear trend from 1955-2003, red is >0.025°C per decade
Other changes consistent with increasing temperature
Observations of global rise in sea level red: reconstructed blue: tide gauges black: satellite
Other changes consistent with increasing temperature
2005
1979 Minimum summer extent (September) NASA
Other changes consistent with increasing temperature Oak Phenology Trends (Timing of Bud Burst)
Badeck et al., 2004
Line of Evidence #4: Models
Diagram from NCAR
Logic connecting emissions to projected climate changes
The most uncertainty in climate projections comes from emissions scenarios
Modeling groups in IPCC AR4
IPCC, 2007
Summary of what we know - Greenhouse gases cause warming by absorbing infrared radiation - Greenhouse gas concentrations are increasing, caused by human emissions - Global temperatures are increasing (0.7 °C = 1.3 °F since 1860) - Temperatures will continue to rise with continued GHG emissions
Anthropogenic Greenhouse Gas Emissions
AR4 WGIII TS
Global totals, anthropogenic emissions, for year 2000
USA – CO2 emissions from fossil fuel combustion (2005)
US EPA
Decreasing 13C strongly suggests that the source of atmospheric CO2 is fossil carbon
Line of evidence #1: Physics
Line of evidence #1: Physics with numbers
Line of evidence #2: Paleoclimate
Where do these data come from??
Paleoclimate to 650,000 years
European Project for Ice Coring in Antarctica
Paleoclimate to 5 million years
Paleoclimate to 65 million years
Line of evidence #3: Observations
Global average observed warming is 0.7 °C (1.3 °F) since 1860.
IPCC, 2007
Line of evidence #3: Observations • Eleven of the twelve years from 1995-2006 were the warmest on record • Average ocean temperature has increased to depths of at least 3 km • Arctic temperatures have increased at twice the global average • Since 1978, average arctic sea ice extent has shrunk by 2.7% per decade • Area covered by permafrost in the Northern Hemisphere has decreased by 7% since 1900 • More intense and longer drought have occurred since the 1970s, particularly in the tropics
IPCC, 2007
Other changes consistent with increasing temperature Increasing global ocean temperatures
Linear trend from 1955-2003, red is >0.025°C per decade
Other changes consistent with increasing temperature
Observations of global rise in sea level red: reconstructed blue: tide gauges black: satellite
Other changes consistent with increasing temperature
2005
1979 Minimum summer extent (September) NASA
Other changes consistent with increasing temperature Oak Phenology Trends (Timing of Bud Burst)
Badeck et al., 2004
Line of Evidence #4: Models
Diagram from NCAR
Logic connecting emissions to projected climate changes
The most uncertainty in climate projections comes from emissions scenarios
Modeling groups in IPCC AR4
IPCC, 2007
Summary of what we know - Greenhouse gases cause warming by absorbing infrared radiation - Greenhouse gas concentrations are increasing, caused by human emissions - Global temperatures are increasing (0.7 °C = 1.3 °F since 1860) - Temperatures will continue to rise with continued GHG emissions
