E.Here New Scientist breaks down what is new in the report，and what it means for humanity’s efforts to cope with a changing climate.A companion article，“How climate change will affect where you live”，highlights some of the key impacts that different regions are facing.What has changed in the new IPCC report?
F.In essence，the predictions are intentionally vaguer.Much of the firlner language from the 2007 report about exactly what kind of weather to expect，and how changes witl affect people，has been replaced with more cautious statements.The scale and timing of many regional impacts，and even the form of some，now appear uncertain.
G.For example，the 2007 report predicted that the intensity of cyclones over Asia would increase by 10to 20 per cent.The new report makes no such claim.Similarly,the last report estimated that climate change would force up to a quarter of a billion Africans into water shortage by the end of this decade.The new report avoids using such firm numbers.
H.The report has even watered down many of the more confident predictions that appeared in the lcaked drafts.References to“hundreds of millions”of people being affected by rising sea levels have been removed from the summary,as have statements about the impact of warmer temperatures on crops.“I think it's gone back a bit，”says Jean Palutikof of Griffith University in Brisbane，Queensland，Australia，who worked on the 2007 report.“That may be a good thing.In the fourth [climate assessment]we tried to do things that weren’t really possible and the fifth has sort of rebalanced the whole thing.”
So do we know less than we did before?
I.Not really,says Andy Pitman of the University of New South Wales in Sydney,Australia.It is just more rigorous language.“Pointing to the sign of the change，rather than the precise magnitude of the change，is scientifically more defensible，”he says.
J.We also know more about what we don’t know,says David Karoly at the University of Melbourne.“There is now a better understanding of uncertainties in regional climate proj ections at decadal timescales(时标).”
Are we less confident about all the impacts of climate change?
K.Not quite.There are still plenty of confident predictions of impacts in the reponv—at least in the draft chapters that were lcaked last year,and which are expected to be roughly the same when they are released later this week.These include more rain in parts ofAfrica，more heatwaves in southem Europe，and more frequent droughts in Australia(see“How climate change will affect where you live”).It also remains clear that the seas are rising.How do we prepare in cases in which there is low confidence about the effects of climate change?
L.That’s exactly what this report deals with.In many cases，the uncertainty is a matter of magnitude，so the choices are not hard.“It doesn’t really matter if the car hits the wall at 70 or 80 kilometres an hour,”says Karoly.“You should still wear your seat belt.”So when it comes to sea.1evel rise or heatwaves，the uncertainty does not change what we need to do：build sea walls，use efficient cooling and so forth.