Intergovernmental Panel on Climate Change will publish in February 2012 a special report, Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. The Summary for Policymakers is available now.
The report itself, and the summary, consider a number of topics from reducing vulnerability and exposure to climate change, sharing risks, etc. I will mention only a few.
The text includes lots of caveats, confidence in the statement (and whether it it is limited by problems with models or limited knowledge of some regions of the world), and sections in the final report where more detailed explanations can be found.
• While natural variability has been and will continue to be important, there has been a shift to more extreme events, as has been predicted, and there is a shift in type.
The mean and shape change, shown here for temperature (both mean temperature and variability are increasing). The number of cold events has not decreased as much as hot events have increased. Over time, the effects of increasing temperature will become more important and there will be fewer of what is today considered an extreme cold event.
There has been an increase in droughts in some areas, decrease in others; ditto for heavy precipitation events. Storm tracks outside the tropics appear to have moved poleward.
• [In a lecture on adaptation—living with the changes we do not prevent, the single most important method of adaptation in most areas is to decrease practices that are bad, independent of climate change. Use water for agriculture more judiciously, protect the coral reefs, reduce pollution, don't build on flood plains, etc.]
Increasing exposure of people and economic assets has been the major cause of the long-term increases in economic losses from weather- and climate-related disasters.
Events can do great damage even when they are not extreme, if the population is vulnerable, or if the effects are compounded (heat and low humidity will increase the numbers of forest fires).
In turn, repeated problems arising from climate change and other causes, such as frequent forest fires, interfere with our ability to adapt in the future.
• It’s going to get worse.
A changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of extreme weather and climate events, and can result in unprecedented extreme weather and climate events.
• The poor pay more, in human life, and as a percentage of GDP.
Economic, including insured, disaster losses associated with weather, climate, and geophysical events are higher in developed countries. Fatality rates and economic losses expressed as a proportion of GDP are higher in developing countries. During the period from 1970 to 2008, over 95% of deaths from natural disasters occurred in developing countries.
Expenditures range from 0.1% of GDP in high-income countries to 0.3% in low-income countries, as of 2006. In small island states, losses between 1970 and 2010 averaged over 1% in many cases, and 8% in the most extreme case.
• Choices that look good today may not look as good tomorrow.
[D]isaster risk management strategies and policies can reduce risk in the short term, but may increase exposure and vulnerability over the longer term. For instance, dyke systems can reduce flood exposure by offering immediate protection, but also encourage settlement patterns that may increase risk in the long-term.
• Change ahead:
—temperature highs now occurring once every 20 years will occur more frequently mid-century (every 3 – 4 years, where I live, in Western North America) and even more often the last couple decades of this century (from 1.5 – 3 years). North Europe will see less change, with today’s 20-year highs exceeded every 5 – 6 years by mid-century, every 3 – 6 years by the end of the century. Mexico and the Amazon will see more dramatic shifts, with current 20-year highs occurring every 2 years or so by mid-century, and every year+ by the end of the century. Globally, the 20-year extremes will be exceeded every 2 – 3.5 years by mid-century, every year or two by the end of the century.
Extreme precipitation events will also be more common, with today’s 20-year events occurring every 12 – 14 years in western North America by mid-century, every 8 – 11 years by the end of the century. Globally, these numbers are 12 – 14 years mid-century, and 7 – 10 years by the end of the century.
• More floods are expected in some areas. In the same locations, or elsewhere, there will be an increase in consecutive dry days, and
droughts will intensify in the 21st century in some seasons and areas, due to reduced precipitation and/or increased evapotranspiration. This applies to regions including southern Europe and the Mediterranean region, central Europe, central North America, Central America and Mexico, northeast Brazil, and southern Africa.
Coasts are at risk due to sea level rise, but so are higher altitudes:
changes in heat waves, glacial retreat and/or permafrost degradation will affect high mountain phenomena such as slope instabilities, movements of mass, and glacial lake outburst floods.
• Climate change will affect our lives in big ways, but it is not the only reason to change:
Extreme events will have greater impacts on sectors with closer links to climate, such as water, agriculture and food security, forestry, health, and tourism. For example, while it is not currently possible to reliably project specific changes at the catchment scale, there is high confidence that changes in climate have the potential to seriously affect water management systems. However, climate change is in many instances only one of the drivers of future changes, and is not necessarily the most important driver at the local scale…
In many regions, the main drivers for future increases in economic losses due to some climate extremes will be socioeconomic in nature. Climate extremes are only one of the factors that affect risks, but few studies have specifically quantified the effects of changes in population, exposure of people and assets, and vulnerability as determinants of loss. However, the few studies available generally underline the important role of projected changes (increases) in population and capital at risk.
See figures SPM.4A and SPM.4B for changing frequency of temperature and precipitation extremes where you live, and figure SPM.5 for more on droughts.
Scientists may not agree with predictions about tropical cyclones.