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Read some of the previews of what the summary from the updating for policy makers from the Intergovernmental Panel on Climate Change (IPCC) would say and you might think much of this climate change business was being overstated. Take the example from page one of Friday’s The Australian illustrated here.
Or this preview story from the BBC earlier in the week on which The Australian (a Murdoch paper) based its coverage:
The draft, which has found its way into my possession, contains a lot more unknowns than knowns.
On the one hand, it says it is “very likely” that the incidence of cold days and nights has gone down and the incidence of warm days and nights has risen globally.
And the human and financial toll of extreme weather events has risen.
But when you get down to specifics, the academic consensus is far less certain.
There is “low confidence” that tropical cyclones have become more frequent, “limited-to-medium evidence available” to assess whether climatic factors have changed the frequency of floods, and “low confidence” on a global scale even on whether the frequency has risen or fallen.
In terms of attribution of trends to rising greenhouse gas concentrations, the uncertainties continue.
Well, the Summary for Policymakers of the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation prepared for this week’s IPCC meeting in Uganda is now available to all 0f us online. Judge for yourself if these findings justify a heading “Review fails to support climate change link.”
CLIMATE EXTREMES AND IMPACTS
Confidence in projecting changes in the direction and magnitude of climate extremes depends on many factors, including the type of extreme, the region and season, the amount and quality of observational data, the level of understanding of the underlying processes, and the reliability of their simulation in models.
Term Likelihood of the outcome
Virtually certain 99-100% probability
Very likely 90-100% probability
Likely 66-100% probability
About as likely as not 33 to 66% probability
Unlikely 0-33% probability
Very unlikely 0-10% probability
Exceptionally unlikely 0-1% probability
Models project substantial warming in temperature extremes by the end of the 21 st century. It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur in the 21st century on the global scale. It is very likely that the length, frequency and/or intensity of warm spells, or heat waves, will increase over most land areas.
It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls will increase in the 21st century over many areas of the globe. This is particularly the case in the high latitudes and tropical regions, and in winter in the northern mid-latitudes. Heavy rainfalls associated with tropical cyclones are likely to increase with continued warming. There is medium confidence that, in some regions, increases in heavy precipitation will occur despite projected decreases of total precipitation in those regions.
Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged.
There is medium confidence that there will be a reduction in the number of extra-tropical cyclones averaged over each hemisphere. While there is low confidence in the detailed geographical projections of extra-tropical cyclone activity, there is medium confidence in a projected poleward shift of extra-tropical storm tracks. There is low confidence in projections of small spatial-scale phenomena such as tornadoes and hail because competing physical processes may affect future trends and because current climate models do not simulate such phenomena.
There is medium confidence that 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. Elsewhere there is overall low confidence because of inconsistent projections of drought changes (dependent both on model and dryness index). Definitional issues, lack of observational data, and the inability of models to include all the factors that influence droughts preclude stronger confidence than medium in drought projections.
Projected precipitation and temperature changes imply possible changes in floods, although overall there is low confidence in projections of changes in fluvial floods. Confidence is low due to limited evidence and because the causes of regional changes are complex, although there are exceptions to this statement. There is medium confidence (based on physical reasoning) that projected increases in heavy rainfall would contribute to increases in local flooding, in some catchments or regions.
It is very likely that mean sea level rise will contribute to upward trends in extreme coastal high water levels in the future. There is high confidence that locations currently experiencing adverse impacts such as coastal erosion and inundation will continue to do so in the future due to increasing sea levels, all other contributing factors being equal. The very likely contribution of mean sea level rise to increased extreme coastal high water levels, coupled with the likely increase in tropical cyclone maximum wind speed, is a specific issue for tropical small island states.
There is high confidence that 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. There is also high confidence that changes in heavy precipitation will affect landslides in some regions.
There is low confidence in projections of changes in large-scale patterns of natural climate variability. Confidence is low in projections of changes in monsoons (rainfall, circulation) because there is little consensus in climate models regarding the sign of future change in the monsoons. Model projections of changes in El Niño – Southern Oscillation variability and the frequency of El Niño episodes are not consistent, and so there is low confidence in projections of changes in this phenomenon
