Climate change science review makes scary bedtime reading

Late last night I sat at the kitchen table reading a new review of the latest climate change science (there wasn't much worth watching on television).  The broad conclusion from the research, written for the Committee on Climate Change, is that although there is uncertainty around the impacts of a warmer planet, the evidence is strong for us doing our utmost to avoid a two degree rise in global average temperatures.

In my last blog I said our one big gripe with the Committee on Climate Change is that they are sticking to recommending emissions reductions that only give a 50:50 chance of avoiding a two degree rise. Here are ten findings from the review that suggest we should aim for a much higher chance of avoiding two degrees. As I write, some developed country negotiators in Cancun are still trying to stitch together an agreement that could lead to a terrifying five degree increase.

 At two degrees

1. Crop production in India could reduce by 10-40 per cent.
2. An additional 1.5 to 2.5 billion people could be at risk from dengue fever due to climate change and population growth.
3. There is a critical risk for drought in south and south-eastern Europe, other areas at risk of drought includes Australia, West Africa, North West Asia and parts of the Americas and Africa. Desertification is mentioned as a particular risk in the Mediterranean, Australia and parts of Africa.
4. There could be an increase of 95,000 people dying in sub-Saharan Africa due to malaria.
5. It is "clear that projections of climate change impacts on forests are now considerably larger than [previously] described". A significant loss of forest cover in Amazonia for a two degree limit is possible.
6. New findings show substantial impacts in tropical regions for ecosystems and species for low levels of temperature change.
7. The West Antarctic ice sheet could collapse: "mechanisms for rapid collapse are possible, relating to retreat of the grounding line, though threshold for such a change are currently difficult to estimate".
8. Some countries will be little affected by a one-metre sea level rise, while "others will be so heavily impacted that their national integrity may be threatened". Egypt could lose 13 per cent of agricultural land, 5.5 per cent of urban areas, and 6.5 per cent of wetlands.
9. There is greater understanding that releases from methane (a potent greenhouse gas) from wetlands is a threat, but "significant uncertainty in this developing area precludes any present estimation of potential thresholds or risk".
10. Some evidence of thawing permafrost observed although "large uncertainties remain in the size of the carbon store, the possible timescale of release and the temperature threshold".

On the optimistic side, it is now thought the Greenland ice sheet is unlikely to collapse at two degrees (although a risk of significant loss at higher tempratures) and Arctic sea ice may reduce by only 70 per cent. It is unlikely that sea level rises of greater than one metre will happen this century (although two metres cannot be ruled out).

Overall the review isn't ideal bedtime reading if you want sweet dreams rather than scary ones, but it does provide a strong motivation to push for the greatest chance of avoiding 2 degree.