To Extremes Dossier on Risk

8/3/2019 To Extremes Dossier on Risk

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TOEXTREMES.ORG

The science of extremes:

Risk

A warmer climate changes the odds of extreme events.

A temperature reached only once every twenty years is likely to be reachedevery two years by the end of the 21st century in most regions. In the northern

areas of the northern hemisphere it is likely to occur once every five years. This isforecast to occur if greenhouse gas emissions continue on their current trajectory.(Kharin, 2007)

What determines the risk of climate-related disasters

The inherent risk of any one climate or weather disaster depends on three elements:o The nature of the disturbance (how long a heat wave, how severe the flooding)o The presence of people in the area (say, settlements along rivers or coasts)o The vulnerability of those people (warning systems, infrastructure for response,

etc.)

You dont need a hugely extreme event. You could have a series of smaller events buit comes in the context of great societal vulnerability, and people are unprepared for thadditional stressor that comes from climate.When you look at how well prepared weare for the disasters were facing now, were behind the eight ball already. So that adda lot of urgency. (Geographer Susi Moser, Extreme Events report editor)

During the period of 1970 to 2008, 95% of deaths from natural disasters occurred indeveloping countries (Extreme Events report summary)

Increasing exposure of people and economic assets has been the major cause of thelongterm increases in economic losses from weather- and climate-related disasters (higconfidence)Long-term trends in economic disaster losses adjusted for wealth andpopulation increases have not been attributed to climate change, but a role for climatechange has not been excluded (medium evidence, high agreement)(Extreme Eventsreport summary)

The past is not prologue

For flooding and droughts, historical records used to dictate the future in planning fordisasters. Now there no analogy in past records (Stationarity is Dead: Wither WaterManagement Milly et al., 2008).
http://journals.ametsoc.org/doi/abs/10.1175/JCLI4066.1http://journals.ametsoc.org/doi/abs/10.1175/JCLI4066.1http://journals.ametsoc.org/doi/abs/10.1175/JCLI4066.1http://journals.ametsoc.org/doi/abs/10.1175/JCLI4066.1


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What risk is acceptable?

Signed by the US, China and 193 other nations, the 1994 United Nations FrameworkConvention on Climate Change defines its goal as aiming to reduce the risk of

dangerous anthropogenicinterference (italics added):

ARTICLE 2: OBJECTIVE The ultimate objective of this Convention and anyrelated legal instruments that the Conference of the Parties may adopt is toachieve, in accordance with the relevant provisions of the Convention,stabilization of greenhouse gas concentrations in the atmosphere at a level thatwould prevent dangerous anthropogenic interferencewith the climate system.Such a level should be achieved within a time-frame sufficient to allowecosystems to adapt naturally to climate change, to ensure that food productionis not threatened and to enable economic development to proceed in asustainable manner.

Along these lines, in 2007 the European Union formally adopted a goal of limitinganthropogenic warming to 2 deg C. A number of papers have sought to analyze andcriticize that goal. Timothy Lenton, for one, criticizes the 2 degree goal as it could missthe possible regional effects of warming that occur at lower levels of warming:

Global average warming is not the only kind of climate change that is dangerous,and long-lived greenhouse gases are not the only cause of dangerous climatechange. Target setters need to take into account all the factors that threaten to tipelements of Earth's climate system into a different state, causing events such asirreversible loss of major ice sheets, reorganizations of oceanic or atmosphericcirculation patterns and abrupt shifts in critical ecosystems.

Such large-scale discontinuities are arguably the biggest cause for climate concerAnd studies show that some could occur before global warming reaches 2 deg C,whereas others cannot be meaningfully linked to global temperature.

Whats dangerous is a judgment call central to the assessment of risk by society, andnot science.

Managing risk includes Long-term steps (e.g., reduce poverty, increase literacy/communication, reduce

chance of dangerous human-caused warming)

Medium term steps (e.g., strengthen disaster response services) Short term efforts (e.g., improve disaster monitoring)


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The following slides are from the official IPCC presentation on the Extreme Events report:


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Past is notprelude

Documents

To Extremes Dossier on Risk