Update on Climate Science. Professor Richard Betts, Met Office

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1 Update on Climate Science Professor Richard Betts, Met Office

2 The science of climate change Crown copyright Met Office Prof Richard Betts Head of Climate Impacts Research

3 Crown copyright Met Office Observing climate

4 There are many other indicators of climate change Arctic sea-ice extent and northern hemisphere spring snow cover have decreased Glaciers and ice sheets worldwide are shrinking Virtually certain that the upper ocean has warmed between , and likely since 1870s Sea-level rise is unusually high over the last 2000 years

5 Crown copyright Met Office Investigating the causes of warming: how do we do a controlled experiment on the Earth?

6 Crown copyright Met Office Computer modelling of climate: experiments on the Earth in a virtual reality

7 Crown copyright Met Office Observing climate

8 Explaining climate change Natural & man-made factors Natural factors only Observations Crown copyright Met Office

9 Human contribution to changes in climate extremes Phenomenon Fewer cold days and nights More hot days and nights Global changes since 1950 Very likely Very likely Human contribution Very likely Very likely Increase in heat waves Medium confidence Likely Increase in heavy precipitation Likely Medium confidence Increase in drought Low confidence Low confidence Increase in tropical cyclone activity Low confidence Low confidence

10 Crown copyright Met Office

11 Crown copyright Met Office Sawyer (1972)

12 Climate forecasts & scenarios: near-term & long-term?? Internal variability Humaninduced trend? Crown copyright Met Office

13 Crown copyright Met Office Pooh Sticks: an example of predictable forced trend (river flows downhill) and hard-to-predict internal variability (which stick will win?)

14 Climate forecasts & scenarios: near-term & long-term?? Internal variability Humaninduced trend? Crown copyright Met Office

15 Projections of global warming by a number of climate models IPCC (2013)

16 Current global emissions are following the IPCC high scenario Friedlingstein et al (2014)

17 Sea-level rise will continue Global average sea level will rise during the 21 st century, and it is very likely that it will rise faster than it has during the last 40 years. Thermal expansion accounts for 30-55% of the total, with melting of glaciers giving the second largest contribution. RCP4.5 It is likely that reductions in the Greenland and Antarctic ice sheets will contribute to sea level rise by m by 2100.

18 Additional contributions from the ice sheets? During last interglacial, high confidence that maximum global mean sea level was 5-10 m higher than present. Only collapse of marine based sectors of the Antarctic Ice Sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21 st century. Medium confidence that this additional contribution would not exceed several tenths of a meter of sea level rise during the 21 st century.

19 Distribution of net population displacement over the twenty-first century by region assuming no protection for a 0.5 m (grey bars) and a 2.0 m (black bars) rise in sea level. Nicholls R J et al. Phil. Trans. R. Soc. A 2011;369:

20 Quantifying uncertainties in global and regional impacts Projected change in streamflow at 2 C warming relative to : Inter- Sectoral Impacts Model Intercomparison Project (ISI-MIP) Crown copyright Met Office Schewe et al (2013)

21 Can terrestrial species shift to keep pace with climate change?

22 Summary Met Office Hadley Centre maintains key observational datasets Computer climate model (same as weather forecast model) used to explain observed changes and estimate future change Warming of last few decades broadly predicted by Met Office in early 1970s Considerable uncertainties in future projections of impacts of different greenhouse gas emissions scenarios but can inform risk assessment On short timescales, internal variability dominates so do not always assume long-term trends will be seen over a few years Crown copyright Met Office

23 Temperature difference ( o C) relative to Challenge of near-term climate forecasts Global annual temperature

24 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

25 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

26 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

27 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

28 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

29 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

30 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

31 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

32 Challenge of near-term Temperature difference ( o C) relative to climate forecasts Global annual temperature

33 Crown copyright Met Office Decadal forecast