Human fingerprints on our changing climate Neil Leary Changing Planet Study Group June 28 – July...

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.