Human fingerprints on our changing climate
Neil LearyChanging Planet Study GroupJune 28 – July 1, 2011
Cooling the Liberal Arts CurriculumA NASA-GCCE Funded Project
Predictions from Earth sciences• Emissions of CO2 and other GHGs from human activities will increase their
concentrations in the atmosphere– Ratio of C12/C13 in atmosphere
• Global avg surface air temperatures will rise• Time pattern of warming would correlate w/ timing of GHG concentration
changes – – adjusting for changes in human & volcanic aerosols, changes in solar output– More warming in winter than summer– More warming at night than day
• Spatial pattern of warming– Widespread; expect warming to dominate on all continents– Greater warming over land than oceans– Greater warming at high northern latitudes
• Warming in troposphere, cooling in stratosphere• Warming oceans
Rising atmospheric temperature (also in
oceans & upper atmosphere)
Rising sea level
Reductions in NH snow cover
Source: IPCC 2007 WG1, Figure SPM.3
Hansen et al, 2005 copied from UCS, http://www.ucsusa.org/global_warming/science_and_impacts/science/global-warming-human.html
Upper: Comparison of changes relative to 1900 in 5-year moving average of observed global mean surface temperature with simulated temperature from DOE PCM model.
Lower: Model simulations of the individual effects of greenhouse gases, solar radiation, stratospheric and tropospheric ozone changes, volcanic emissions and sulfate emissions.
Source: Meehl et al, 2004.
Models vs observations
Human + natural forcings
Natural forcings only
Source: IPCC 2007 WG1 (Figure 9.5)
IPCC 2007, Fig 9.1. Zonal mean atmospheric temperature change, 1890 - 1999. a) solar, b) volcanoes, c) ghgs, d) trop. & strat. ozone, e) sulfate aerosol, f) all forcings
IPCC (2007), chapter 10, Figure 10.8. Multi-model mean annual surface warming relative to 1980-1999
IPCC (2007), Figure 5, WG1 SPM
IPCC (2007), chapter 10, Figure 10.8. Multi-model mean annual surface warming relative to 1980-1999
IPCC (2007), Figure 7 SPM. Multi-model average changes in DJF and JJA precipitation for 2090-2099 relative to 1980-1999.