http://www.swopnet.com/engr/londonsewers/londontext1.html Typical cesspit, with access from the street By the early 18th Century nearly every residence had a cesspit beneath the floors. In the best of homes the nauseating stench permeated the most elegant parlor. Indoor odors were often worse than of the garbage- and manure- filled streets. While noxious fumes were ignored by most people, it was fear of "night air" laden with coal smoke and sulfurous industrial fogs which alarmed the Climate Change Week 7 Lecturer: John Todd Ecosystem Processes 16 April 2002 Why start a lecture on climate change with a diagram of a cesspit? • Disposal of waste has always been a problem for human societies. • We are learning the importance of liquid and solid waste disposal; and we have had some success in controlling some waste discharged into the atmosphere. • We now need to learn that with so many humans we need to limit all wastes released to the atmosphere. Population World Population 7 Billions of people 6 5 4 3 2 1 0 1600 1700 1800 1900 Ye ar 2000 2100 We have learnt not to dump solid and liquid wastes into our rivers. But we discharge some 20 billion tonnes of carbon dioxide into the atmosphere each year. Facts and Speculation • • • • • • Changes to atmosphere Impact on radiation Complicating factors Observed warming Uncertainty contributes to lack of action Some possible futures First Some Facts 1. The chemical composition of the atmosphere is changing 2. It is almost certain that human activities are contributing to these changes 3. The average surface temperature is warming 4. But some argue that point 3 is not linked to points 1 and 2 Changes to atmosphere Carbon Dioxide CO2 Ice cores allow CO2 analysis back 400,000 years Now Cape Grim, Tasmania’s ‘baseline’ monitoring station Carbon dioxide (parts per million) Cape Grim, Tas is one of the important global monitoring sites for climate change gases. 1970 1975 1980 1985 1990 1995 2000 2005 There are at least 30 gases, released by human activities, increasing in the atmosphere that influence the heat escaping by radiation. Air reaching Cape Methane (parts per billion) Grim from the west 1720 1700 and south-west has 1680 1660 travelled ¾ of the 1640 1620 way round the 1600 1580 world without 1560 passing over land. 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 375 370 365 360 355 350 345 340 335 330 325 Gases that interact with energy flow out of the atmosphere – greenhouse gases CO2 Sunlight in 0.7 Infrared out Wavelength 10 20 25ooCC CH4 N2O Long time scales • The energy reaching the Earth each day is large, so one might expect quick changes • But we have seen how massive the atmosphere is 5 x 1015 tonnes • The earth itself is 6 x 1021 tonnes • These numbers are so large they are difficult to comprehend, but the point is, it will take a long time to heat the Earth up and a long time for it to cool off again. Carbon Balance – annual flows Units 109 tonnes of carbon About 1 unaccounted for 700 in atmosphere increasing by about 2 per year Burning fossil fuels 5 50 1 3 600 800 7000 40,000 3000 1998 hottest ever 2001 second hottest Uncertainties • Will climate change lead to more storms, more droughts, more floods? • Will feedback processes, such as increased cloud, faster plant growth, etc. off-set the changes? • Will other changes accelerate the warming, e.g. less ice and snow, CO2 release from oceans, melting of tundra etc.? No trends are obvious Tropical cyclones in the Australian Region Maybe the proportion of intense storms is greater? Source: Bureau of Meteorology Some of the uncertainties • If it gets warmer, there will be more evaporation. • This will alter the water cycle slightly, but we have seen how much energy the evaporation and condensation of water transfers to the atmosphere. • How will this change local weather? • Will there be more clouds? • Will there be more rain? Implications for your professional work • Will need informed people in many disciplines who can deal with this issue sensibly. • Reduce the emissions of climate change gases. • Facilitate adaptation to changes in weather patterns Summary • We are altering the chemical composition of the Earth’s atmosphere. • The Earth is warming. • The impact this will have on the processes we have covered in this series of lectures is unknown – – – – Energy flow/radiation Global circulation Weather Water cycle Know definitions of identified words Exam • Atmospheric composition, temperature • Radiation balance • Global circulation • Water in atmosphere • Weather • Climate change Need to understand the basics Possible question Possible question Possible question Provides examples for above three topics Also examples, but not the topic of a question Will be one essay question Next Week • Professor Jamie Kirkpatrick • Weathering and erosion • Chapter 13 of Christopherson.