Remarks by Graham Cogley 30 March 2014

J. Graham Cogley, Geography, Trent University, Peterborough, Canada

705-742-0317 gcogley@trentu.ca www.trentu.ca/geography/glaciology

Climate Change 2014: Impacts, Adaptation and Vulnerability

Contribution of Working Group II to the Fifth Assessment Report of the

Intergovernmental Panel on Climate Change

(IPCC AR5 WGII)

IPCC AR5 – Outline The chain linking the greenhouse gases to their impacts is long and

complex, but we are all but certain that the impacts will be widespread and consequential. I will discuss a few:

• Glacier melting and its implications for society

• Reduced access of people to freshwater

• Increased flooding and connections to climate change

Morteratsch Glacier, Alps, circa 1900 Credits: Jürg Alean

Morteratsch Glacier, Alps, 2012

IPCC AR5 and Glacier Meltwater

Published mass balances for Himalayan glaciers (blue boxes show uncertainty, negative numbers mean loss); global average in orange Chapter 3 and Summary for Policymakers, IPCC AR5 Working Group II

Most glaciers are too big even for the present climate; future warming will only increase rates of loss and (eventually) disappearance This means more water in coming decades (faster melting rates), but big trouble later (fewer glaciers)

Glaciers are essential contributors to water supply in several regions, such as Peru, the Alps and central Asia, but the Himalayas stand out

IPCC AR5 and Freshwater Resources

Human access to freshwater resources will continue to diminish: more people – farmers, city dwellers, skiers, etc. – will pay more for water, or will go short if they cannot pay

Schewe, J., and 24 others, 2014, Multimodel assessment of water scarcity under climate change, Proceedings of the National Academy of Science, 111(9), 3245-3250; Figure S6.

IPCC AR5 and Floods A high-carbon future will expose more people to the risk of floods

Averages over 11 climate models No population growth

Hirabayashi, Y., and 6 others, 2013, Global flood risk under climate change, Nature Climate Change, 3, 816-821.

At the moment we are on the orange path Switching to the green path makes a difference!

IPCC AR5 – A personal favourite

Questions like “Was this flood caused by global warming?” have been unanswerable up to now However, using enormous computing power, a recent study showed that the UK floods of autumn 2000 were 2-3 times more likely to have occurred in a world with global warming than one without

Pall, P., and 7 others, 2011, Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000. Nature, 470, 382-385.

IPCC AR5 – Summary

• Observed impacts are widespread and consequential

• Risks are much greater in a world of continued high emissions, which increase the likelihood of severe impacts that may be complex, surprising, or irreversible

• Impacts and risks will grow steadily worse over decades

• Reducing emissions now can substantially reduce risks in the second half of the century

• Not all the news is bad – opportunities for adaptation are there for the taking

Field, C., V. Barros and 69 others, 2014, Summary for Policymakers, IPCC AR5 Working Group II

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Notes for IPCC Presentation – Graham Cogley, Science Media Centre, 30 March 2014 Slide 2 The chain linking the greenhouse gases to their impacts is long and complex, but we are all but certain that the impacts will be widespread and consequential. I will discuss a few: • Glacier melting and its implications for society • Reduced access of people to freshwater • Increased flooding and connections to climate change We are very confident that the impacts and risks will grow steadily worse over decades, but equally confident that reducing emissions now can substantially reduce risks in the second half of the century Not all the news is bad – opportunities for adaptation are there for the taking Slide 3 The glaciers are doing just what we would expect – sending the same message as the thermometers at weather stations This is a mixture of good news and bad for water resources: more water in coming decades (faster melting rates), but big trouble later (fewer glaciers) Glaciers are essential contributors to water supply in several regions, such as Peru, the Alps and central Asia, but the Himalayas stand out The Himalayan glaciers were controversial after the Fourth Assessment, but the IPCC has quietly cleaned up its act – approving a detailed protocol for handling errors and correcting its Himalayan mistake

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In fact the Himalayan glaciers are about average, although they present special problems such as the unpredictable bursting of meltwater lakes Slide 4 Human access to freshwater resources will continue to diminish: more people – farmers, city dwellers, skiers, … – will pay more for water, or will go short if they cannot pay The greater the warming, the greater the diminution: for each degree of global warming, roughly an additional 7% of the global population (those in the red bands) will see a decrease of renewable water resources by at least 20% Slightly more people will enjoy increased water resources, but most of them live where there is already enough water Slide 5 Extreme events are getting more extreme, more frequent or both The number of people exposed annually to floods of the size of the 20th-century 100-year flood becomes three or more times greater by 2100 for very high than for very low emissions Slide 6 Climate science never deals in certainties – only in likelihoods, and preferably over large regions and long periods The question “Was this flood caused by global warming?” has been unanswerable up to now, but in a major step forward one study produced the answer “Yes” – by running two sets of climate simulations, one with and one without the anthropogenic contribution, and calculating the “attributable risk” (at enormous cost, unfortunately) 20th-century emissions of greenhouse gases made the floods in England in autumn 2000 about 2–3 times more likely Working Group II assessed this result as compelling – a word that scientists use very sparingly

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Slide 7 The chain linking the greenhouse gases to their impacts on human society is long, and hard to unravel, but several conclusions are all but certain: •Observed impacts are widespread and consequential •Risks are much greater in a world of continued high emissions, which increase the likelihood of severe impacts that may be complex, surprising, or irreversible •Impacts and risks will grow steadily worse over decades •Reducing emissions now can substantially reduce risks in the second half of the century •And not all the news is bad – opportunities for adaptation are there for the taking