Human fingerprints on our changing climate Neil Leary Changing Planet Study Group June 28 – July 1, 2011 Cooling the Liberal Arts Curriculum A 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, 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, a) solar, b) volcanoes, c) ghgs, d) trop. & strat. ozone, e) sulfate aerosol, f) all forcings

IPCC (2007), chapter 10, Figure Multi-model mean annual surface warming relative to

IPCC (2007), Figure 5, WG1 SPM

IPCC (2007), chapter 10, Figure Multi-model mean annual surface warming relative to

IPCC (2007), Figure 7 SPM. Multi-model average changes in DJF and JJA precipitation for relative to