1 INTRODUCTION
1.3 C LIMATE CHANGE , CLIMATE IMPACTS AND CLIMATE - RELATED EVENTS
Various metrics or indicators are used to monitor how the climate has and is changing (Blunden, & Arndt 2013), and a number of these are shown in figure 1.3. All of these indicators in figure 1.3 are consistent with what one would expect under a warming world.
Typically, however, the indicator of choice when searching for evidence of a changing climate is the global annual mean surface temperature change, and this is shown in figure 1.4. Clearly, observations of surface temperature show that the Earth has warmed, and over the period 1880 to 2012 the global average land and ocean surface temperature has warmed by 0.85oC (IPCC 2013). Figure 1.4 also shows that while the annual average may display a spiky pattern – with some years being warmer or colder than the preceding one, when taking a longer view and averaging over a decade, the last three decades have been successively warmer than any preceding decade since 1850 (IPCC 2013).
Climate model projections indicate that the Earth will continue to warm over the course of the 21st century. Projections from the AR5 suggest an increase in global mean surface temperature in the time period 2081-2100 of 0.3oC to 4.8oC, relative to 1986-2005 (IPCC 2013). As the Earth warms, this also has implications for sea level rise. Projections of global mean sea level rise from the AR5, suggest that global mean sea level in the time period
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2081-2100 may increase by between 0.26 m and 0.82 m, relative to levels in the time period 1986-2005 (IPCC 2013).
Clearly, these changes in climate will have a range of impacts on economic, social, and ecological systems. Figure 1.5 provides a summary of potential global climate impacts in a number of economic sectors, for a range of changes in global annual mean surface temperature. These impacts are summarised at the global level, and are intended to provide examples that will help stimulate awareness and analytical thought about how a given organisation may be affected by these and other impacts, rather than trying to be specific about what may happen in a given region. A summary of changes in climate and potential impacts in Germany is available in Zebisch et al. (2005).
The way in which an organisation may be affected by changes in climate is not only through direct changes in climate variables such as temperature and precipitation, but also changes in extreme weather events, such as heatwaves, droughts, storms, flooding and wildfires. A changing climate may influence the frequency and magnitude of such extreme events (IPCC 2012). As such, under a changing climate these events may either serve to exacerbate existing climate risks, and/or generate new ones, that an organisation will need to adapt to.
To aid the clarity of the text in this guidebook, we use the term climate-related event throughout, to refer to both weather events and extremes, and the direct changes in individual climate variables that may generate impacts in different economic, social, and ecological systems.
Figure 1.2 Schematic of the different methodological structures of the conventional “top-down” or impacts-first, and “bottom-up” or thresholds-first, approaches to adaptation.
Source: Lal et al. (2012).
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Figure 1.3 Multiple observed indicators of a changing global climate: (a) Extent of Northern Hemisphere March-April (spring) average snow cover; (b) extent of Arctic July-August-September (summer) average sea ice; (c) change in global mean upper ocean (0–700 m) heat content aligned to 2006−2010, and relative to the mean of all datasets for 1970; (d) global mean sea level relative to the 1900–1905 mean of the longest running dataset, and with all datasets aligned to have the same value in 1993, the first year of satellite altimetry data. All time-series (coloured lines indicating different data sets) show annual values, and where assessed, uncertainties are indicated by coloured shading. Source: IPCC (2013).
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Figure 1.4 (a) Observed global mean combined land and ocean surface temperature anomalies, from 1850 to 2012 from three data sets. Top panel: annual mean values. Bottom panel: decadal mean values including the estimate of uncertainty for one dataset (black).
Anomalies are relative to the mean of 1961−1990. (b) Map of the observed surface temperature change from 1901 to 2012 derived from temperature trends determined by linear regression from one dataset (orange line in panel a). Trends have been calculated where data availability permits a robust estimate (i.e., only for grid boxes with greater than 70% complete records and more than 20% data availability in the first and last 10% of the time period). Other areas are white. Grid boxes where the trend is significant at the 10% level are indicated by a + sign. Source: IPCC (2013).
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Figure 1.5 Illustrative examples of global impacts projected for climate changes (and sea level and atmospheric carbon dioxide where relevant) associated with different amounts of increase in global average surface temperature in the 21st century. The black lines link impacts, dotted arrows indicate impacts continuing with increasing temperature. Entries are placed so that the left-hand side of the text indicates the approximate onset of a given impact. Quantitative entries for water stress and flooding represent the additional impacts of climate change relative to the conditions projected across the range of Special Report on Emissions Scenarios (SRES) scenarios A1FI, A2, B1 and B2. Adaptation to climate change is not included in these estimations. All entries are from published studies recorded in the chapters of the Assessment. Confidence levels for all statements are high. Source: IPCC (2007c).