Transcript Slide 1
Global Warming Briefing for KSL Television Lis Cohen University of Utah [email protected] www.WeatherOutreach.org Today’s Topics • Temperature Trends • What is Global Warming? – Causes – Uncertainties • Consequences of Global Warming • What can people do about this problem? Data Sources • The 2007 IPCC (Intergovernmental Panel on Climate Change) report – Includes • • • • • • • 2,500 + scientific expert reviewers 800+ contributing authors 450+ lead authors from 130+ different countries 6 years of work 4 volumes 1 report • Scientific Literature • Presentations from experts at the University of Utah – Dr. Dave Chapman, Dr. Tim Garrett, Dr. Gerald Mace, Dr. Thomas Reichler Temperature Analysis • “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level” (IPCC report 2007). Contributions to Sea Level Rise Long-term Changes in Climate • Long-term changes are observed at: – Continental Scales – Regional Scales – Ocean basin Scales • These changes include: – – – – – Changes in Arctic temperatures and ice Widespread changes in precipitation amounts Ocean salinity Wind patterns Aspects of extreme weather • • • • including droughts heavy precipitation heat waves intensity of tropical cyclones - 2007 IPCC report What can influence the climate? • Changes in these factors alter the energy balance of the climate system: – The atmospheric abundance of greenhouse gases and aerosols – Solar radiation – In land surface properties -2007 IPCC Report The Greenhouse Effect Effects of changing the amounts of Greenhouse Gases • These changes are expressed in terms of radiative forcing, which is used to compare how a range of human and natural factors drive warming or cooling influences on global climate. LOSU = level of understanding RF = Radiative Forcing Error bars Additional forcing factors not included here are considered to have a very low level of scientific understand. How is the sun affecting climate change? The effect of the sun’s variations accounts for +.12 W/m2. There is very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W/m2. Natural Climate Variability because of the sun has been not very significant. How do we know that this is not a normal cycle? We use past climate data and compare influencing factors. How do we know about past climates? • Tree Rings – Growth is controlled by temperature, precipitation and sunlight • Pollens – give a good indication of what was living at the time indicating a temperature range • Ice and sea bed cores – Gasses in bubbles, dust, isotopes, accumulation rate • The fossil record • Coral beds Note: Uncertainties generally increase with time into the past due to increasingly limited spatial coverage. Paleoclimate Information “Paleoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years.” “The last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to 4 to 6 meters (13-20 feet) of sea level rise.” -2007 IPCC Report What has Changed and what has Not Changed? Aspects of climate that have NOT changed • Day night temperature differences have remained constant. Both the maximum and minimum temperatures have increased at the same rate. The trends are highly variable from one region to another. • Antarctic sea ice extent continues to show inter-annual variability and localized changes but no statistically significant average trends, consistent with the lack of warming reflected in atmospheric temperatures averaged across the region. • There is insufficient evidence to determine whether trends exist in – Meridional overturning circulation of the global ocean – Small scale phenomena • • • • Tornadoes Hail Lightning Dust-storms Consequences of Global Warming Ward Hunt Ice Shelf, 2002 Trend of Less Ice • Many ice bodies from the poles to the tropics are in retreat. • Polar warming in 2100 may reach levels of 130,000 years ago, when sea levels were several meters above today. Larsen B ice shelf, Antarctica ca. 100 x 80 miles Feb. 17, 2002 Mar. 5, 2002 Muir Inlet, Alaska 1941 Glacier Bay National Park and Preserve 2004 National Snow and Ice data center http://nsidc.org/cgi-bin/gpd_run_pairs.pl Arctic Polar Ice Cap 1979 2003 http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html • Since 1979, the size of the summer polar ice cap has shrunk more than 20 percent. • On Sept. 21, 2005, sea ice extent dropped to 2.05 million sq. miles, the lowest extent yet recorded in the satellite record. • This loss is twice the size of Texas. NASA Global Warming 1. Warming is real. 2. Humans are contributing to the warming. 3. Feedback system is complex. 4. Greenhouse gas emissions are growing; residence times are long. 5. Consequences of warming will not be easy for human life. How can everyone help? Vote for politicians that strongly support the environment! Other ideas… Carpool When You Can Reduce Garbage Plant a Tree Insulate Your Water Heater Replace Old Appliances Weatherize Your Home Use a Push Mower Unplug Un-Used Electronics Put on a Sweater Insulate Your Home Air Dry Your Clothes Switch to a Tankless Water Heater Switch to Double Pane Windows Buy Organic Food Bring Cloth Bags to the Market Use Compact Fluorescent Bulbs Inflate Your Tires Change Your Air Filter Fill the Dishwasher Use Recycled Paper Adjust Your Thermostat Check Your Water heater Change the AC Filter Take Shorter Showers Install a Low-Flow Showerhead Buy Products Locally Buy Energy Certificates Buy Minimally Packaged Goods Buy a Hybrid Car What you at KSL can do! • Talk to your viewers about climate change and let them know what they can do to help! – There are many events in Salt Lake about climate change (you can cover them). – Talk with politicians who have worked on the issue. – Interview scientists at the University of Utah (I can help you with this). • Get the ball rolling and see what questions and concerns your viewers have and answer them. • Try to get rid of their misconceptions about climate change. • Talk to your viewers about climate change (Repeated for emphasis )! References • Climate Change 2007: The Physical Science Basis. Intergovernmental Panel on Climate Change. • Garrett, T. “Rapid Arctic Climate Change Forcing the Feedbacks.” 2007. • Chapman, D. “Global Warming – Just Hot Air?” 2006. • Thank you! Questions? Lis Cohen: [email protected]