Weather Condition of the atmosphere at any particular time and place Air temperature, air pressure, humidity, clouds, precipitation, visibility, wind Climate Accumulation of daily and seasonal weather events over a long period of time “Average weather” Wisconsin Initiative on Climate Change Impacts 2011

What is the Greenhouse Effect? Earth: 400 ppm CO 2 Venus: 965,000 ppm CO 2 Venus: 460  C, hotter than Mercury, despite 1/4 of solar irradiance Both Good and Bad

Which is the most abundant greenhouse gas on Earth? National Center for Atmospheric Research

Primary greenhouse gases: - Water vapor (#1) (<1 year) - Carbon dioxide (100s years) - Methane (10 years) - Nitrous oxide (100 years) - Ozone (<1 year) - Hydrofluorocarbons (1000s years) - Chlorofluorocarbons (100s years) National Center for Atmospheric Research

Global warming art Year 2000 #1 #2 #3

Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5); NOAA; Florida Center for Environmental Studies Atmospheric Levels of Carbon Dioxide Atmospheric Levels of Methane Accelerated trend : ppm/year : ppm/year Concentrations are increasing Pre-Industrial Era ≈ 280 ppm June 2014 ≈ 400 ppm (keelingcurve.ucsd.edu) Note the distinct seasonal cycle: “Breath of the biosphere”

Fleagle & Businger Absorption Spectrum: Amount of Radiation Absorbed at a Given Wavelength VISIBLE ULTRAVIOLET (Shortwave) INFRARED (Longwave) Greenhouse gases primarily absorb longwave (infrared) radiation Not absorbed Absorbed

Greenhouse gases Greenhouse Effect Some of the infrared radiation passes through the atmosphere but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds. The effect of this is to warm the Earth’s surface and the lower atmosphere (IPCC AR4 WG1). Shortwav e Longwave Sun = hot = emits shortwave (UV) radiation Earth = cool = emits longwave (IR) radiation Wien’s Law: Wavelength inversely related to temperature

National Climate Assessment; Global Carbon Project; Boden et al Human-induced changes in the global carbon budget since the beginning of the Industrial Revolution. Emissions from fossil fuel burning are the dominant cause of the steep rise from 1850 to Global carbon emissions from burning coal, oil, and gas and producing cement during These emissions account for about 80% of the total emissions of carbon from human activities, with land-use changes accounting for the other 20%.

Patz et al Carbon dioxide emissions Predicted mortality for due to malaria, malnutrition, diarrhea, flooding related to climate change Climate change is an ethics issue China 26% U.S. 17% European Union 13% China 26% U.S. 17% European Union 13%

IPCC AR5 Each decade is subsequently warmer “Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since In the Northern Hemisphere, was likely the warmest 30-year period of the last 1400 years.” – IPCC AR5 “The globally averaged combined land and ocean surface temperature data….show a warming of 0.85°C over the period of ” – IPCC AR5 Note the distinct interannual and decadal variability, in addition to the long-term trend

Claim: But this last winter was brutally cold, so global warming is not happening. Surface air temperature anomalies (°C) during December 2013 – April 2014 Only cold over central North America….most other places in the world were warm, especially the Arctic. Histogram of surface air temperature anomalies (°C) during December 2013 – April 2014 for all global grid cells During those 5 months, 66% of the world was warmer than normal and only 34% was colder than normal.