OH, HERE WE GO AGAIN… ANOTHER BORING GLOBAL WARMING RANT

1. SEEMS TO ME, THE ICE USED TO BE A LOT THICKER THIS TIME OF YEAR… OH, HERE WE GO AGAIN… ANOTHER BORING GLOBAL WARMING RANT OH, PLEASE… CAN YOU POINT TO ANYTHING THAT SHOWS IT’S AS DANGEROUS TO ME AS THEY CRACK IT UP TO BE? YOU MEAN DESPITE THE MOUNTAIN OF HARD EVIDENCE, YOU STILL DON’T BELIEVE IT?

2. Effects of global warming on humans (interpreted broadly)

4. Wildfires have consumed increasing areas of western U.S. forests in recent years, and fire-fighting expenditures by federal land-management agencies now regularly exceed US$1 billion/year. Hundreds of homes are burned annually by wildfires, and damages to natural resources are sometimes extreme and irreversible. Recent, very large wildfires (>100,000 ha) burning in western forests have garnered widespread public attention, and a recurrent perception of crisis has galvanized legislative and administrative action.

5. A few examples…

6. Oakland Hills Fire in October 1991 destroyed 2,550 single-family homes, and 37 apartment and condominium units, and was one of the most deadly fires in recent history, killing 25 people including one police officer and one firefighter. It caused an estimated $1.5 billion in direct damage and burned 1,600 acres.

10. In 2003 and again in 2007 there were enormous wildfires near San Diego, each at the end of especially dry years.

11. Were the brutal San Diego wildfires directly caused by global warming? Princeton’s Michael Oppenheimer put it this way: The weather we’ve seen… may or may not be due to the global warming trend, but it’s certainly a clear picture of what the future is going to look like if we don’t act quickly to cut emissions of the greenhouse gases.

12. The next few slides are modified from an important paper that links wildfires to global warming: Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity A. L. Westerling, H. G. Hidalgo, D. R. Cayan, T. W. Swetnam Science 313, 940-943 (2006).

13. Forest wildfire activity in the western US is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in wildfire frequency has focused instead on the effects of 19th- and 20th-century land-use history. Which is most responsible for the recent increases?

14. Competing explanations: Land-use versus climate • Land-use • Fire frequency reduced by livestock grazing and fire suppression methods in the 20th century • Forest regrowth after extensive logging and absence of extensive fires increased the fuel load, making it harder to fight fires. Thus they are bigger and last longer. • Climatic explanations • Increasing variability in moisture conditions (wet/dry oscillations promoting biomass growth, then burning), • And/or a trend of increasing drought frequency, • And/or warming temperatures • have led to increased wildfire activity In some cases these may be complementary.

15. Increased forest wildfire activity. The incidence of large wildfires (>400 ha) in western forests increased in the mid-1980s Subsequently, wildfire frequency was nearly four times the average of 1970 to 1986, and the total area burned was more than six times its previous level. Wildfire frequency is strongly associated with spring and summer temperature.

16. The frequency of fires also correlates with the timing of the spring snowmelt. Early melting is related to temperature. Overall, 56% of wildfires and 72% of area burned in wildfires occurred in early snowmelt years. Only 11% of wildfires and 4% of area burned occurred in late snowmelt years.

17. The length of the wildfire season also increased in the 1980s, both because of earlier ignition and later control of fires.

18. Regardless of past trends, virtually all climate-model projections indicate that warmer springs and summers will occur over the region in coming decades. These trends will reinforce the tendency toward early spring snowmelt and longer fire seasons. This will accentuate conditions favorable to the occurrence of large wildfires, amplifying the vulnerability the region has experienced since the mid-1980s. The Intergovernmental Panel on Climate Change's consensus range of 1.5° to 5.8°C projected global surface temperature warming by the end of the 21st century is considerably larger than the recent warming of less than 0.9°C observed in spring and summer during recent decades over the western region.

19. Current estimates indicate that western U.S. forests are responsible for 20 to 40% of total U.S. carbon sequestration. If wildfire trends continue, much of this carbon will be released, suggesting that the forests of the western United States may become a source of increased atmospheric carbon dioxide rather than a sink, even under a relatively modest temperature-increase scenario. Hence, the projected regional warming and consequent increase in wildfire activity in the western United States is likely to magnify the threats to human communities and ecosystems, and substantially increase challenges in reducing greenhouse gas emissions. This is a good example of positive feedback that accelerates global warming. • increased temperature increases fires; • fires release CO2; • CO2 increases temperature.

20. The interaction of increased temperatures, the mountain pine beetle, and both lodgepole and jack pine trees provides another good example of positive feedback. The adult mountain pine beetle (Dendroctonus ponderosae) is less than one centimeter long. Damaged trees turn red.

21. By the end of 2006, the mountain pine beetle (Dendroctonus ponderosae) had ravaged 130,000 square kilometers of forest in western Canada. Though not the first time an outbreak has occurred in the region, the latest is an order of magnitude larger than any previous attack and brings the total area of forest destroyed between 1997 and 2007 to 13 million hectares. Beetle populations have exploded because a series of mild winters has allowed the larvae to survive from one year to the next. There is now concern that they will be able to cross the Rocky Mountains and infest timber in the east.

22. Not only is this bad news for the affected trees, whose fate is sealed once the beetle takes hold; the infestation also packs an atmospheric punch. According to a recent report (Kurz et al, (2008) Nature 452, 987-990) the assault on British Columbia's pine trees could cause the region to release more carbon dioxide than it absorbs from the atmosphere over the coming decade. With fewer healthy trees available to absorb the greenhouse gas and more trees decaying and dying, this will further contribute to the warming that is facilitating the pest's territorial spread. According to the new calculations, by 2020 the beetle outbreak alone will have released 270 megatonnes of carbon dioxide into the atmosphere. That's exactly the amount of greenhouse gas emissions that Canada is committed to reducing by 2012 under the Kyoto Protocol. And given that Canada is far from meeting that target, it may be even harder than once thought for the nation to offset its emissions through forest management. Stating the results another way, the predicted emissions are larger than the total CO2 absorbed by all of Canada's managed forest over the last decade.

23. CO2 warming beetles dead trees fire decay live trees Extending the positive feedback cycle further, pines infested by the beetle are much more susceptible to wildfires. Because the fires can spread into adjacent uninfested forest, they will cause even more CO2 release.