Climate Stabilization Targets Emissions, Concentrations, and Impacts over Decades to Millennia (2011) / Chapter Skim
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From page 159... ...
. Rivaling the direct CO2 effects are the impacts of climate changes caused by CO2, in particular changes in air temperature and available soil moisture.
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From page 160... ...
The existing literature identifies several promi nent sources of uncertainty, including those related to the magnitude of local warming per degree global temperature increase, the sensitivity of crop yields to temperature, the CO2 levels corresponding to each temperature level (see Section 3.2) , and the magnitude of CO2 fertilization.
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From page 161... ...
for: Low Latitudes 0 1.2 2.4 3.6 4.8 Mid-High Latitudes 0 1.5 3.0 4.5 6.0 FIGURE 5.1 Average expected impact of warming + CO2 increase on crop yields, without adaptation, for broad regions summarized in IPCC AR4 (left) and for selected crops and regions with detailed studies (right)
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From page 162... ...
. Given the rate of local warming in the Corn Belt relative to global average, this implies an 11% yield loss per °C of global warming (Figure 5.1)
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From page 163... ...
Although most studies have focused on crops, effects of climate change on livestock, aquaculture, and fisheries have also been considered in recent years. Livestock in parts of the world are raised mainly on grain and oilseed crops, in which case impacts will largely follow from the prices of these commodities and the costs of cooling or losing animals during heat waves.
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From page 164... ...
and away from hot tropical nations, with greater flows of food trade from north to south. On average, studies suggest small price changes for cereals up to 2.5°C global temperature increase above pre-industrial levels, with significant increases for further warming, but there is considerable uncertainty around these estimates (see Box 5.2)
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From page 165... ...
First, the yield changes used in these models usually assume considerable levels of farmlevel adaptations, which substantially reduce impacts. For example, in one prominent study cereal prices rose by 150% for a 5.2°C global mean temperature rise if farm-level adaptations were not included.
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From page 166... ...
It is important to note, in interpreting this figure, that the likelihood of inundation from coastal storms may not be proportional with sea level rise. Moreover, the consequences of these storm events calibrated in millions of people in jeopardy from coastal flooding de pend on local population densities and geographic features.
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From page 167... ...
. FIGURE 5.3 Estimates of people flooded in coastal areas attributable to sea level rise along alternative SRES scenarios.
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From page 168... ...
and developing countries (Panel B) correlated with sea level rise along a socioeconomic scenario bitmap that tracks IS92a.
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From page 169... ...
Some are located in important deltas in China where modest sea level rise of 0.3 meters would cause significant loss of land area from inundation and erosion; others are located in eastern and southeastern Asia where 1 m of sea level rise would cause significant loss of land and protective mangroves in addition to putting many people at risk of displacement. The final entry reports recent estimates of associated loss in the habitat of the only tiger population in the world (panthera tigris)
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From page 170... ...
170 CLIMATE STABILIZATION TARGETS FIGURE 5.5 Wetland loss from erosion attributable to sea level rise along three alternative scenarios. Confirmation of the hypothesis that wetland and marshes would be covered to open water by the end of the 5-5.eps century along feasible sea level rise scenarios (current trend up to almost 70cm by 2100.
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From page 171... ...
Hence, understanding how runoff will change in a future climate is the key to understanding how water availability for human use might change. In climate models, runoff is represented by land surface models, which have the primary purpose of partitioning net radiation at the land surface into latent, sensible, and ground heat flux.
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From page 172... ...
is nested within a global model to produce more spatially resolved climate model output. Although dynamical downscaling may be preferred on theoretical grounds (because it is based on physical rather than statistical relationships; its application in practice has been problematic because the computational burden is high, hence the number of RCM runs that can be performed for different global models is small.
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From page 173... ...
We then computed runoff changes as percentages per degree C of global warming, and took the median over models and global temperature changes of 1°C, 1.5°C, and 2°C. We also computed equivalent standard errors of the medians (see Table 5.3)
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From page 174... ...
for IPCC AR4 GCM output from A2, A1B, and B1 simulations for each basin as derived from 30-year runoff averages centered on the years for which the global average (for each of 23 models and the 3 emissions scenarios) were 1°C, 1.5°C, and 2°C minus the 30-year model average runoff for 1971-2000, divided by the global temperature change.
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From page 175... ...
Our overall conclusion therefore is that streamflow in many temperate river basins outside Eurasia will decrease as global temperature increases, with the greatest decreases in areas that are currently arid or semi-arid. Streamflow across most of the United States will decrease, although there is considerable disagreement among models aside from the Southwest, where most models project decreases, and Alaska, where most models project increases.
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From page 176... ...
For example, climate variables account for more than 80% of the variance in annual area burned in the boreal for ests of western North America between 1960-2002 (Balshi et al., 2009) ; climate variables and vegetation type account for two-thirds of the variance in area burned in the western United States (Littell et al., 2009)
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From page 177... ...
The empirical models account for, on average, two-thirds of the variance of the wildfire area burned in the 16 ecoprovinces that comprise the western United States (cross-validated)
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From page 178... ...
Hence, the full suite of AR4 climate models must be employed to project the probability of wildfire changes -- throughout the globe. Second, although both models show increasing temperature and decreasing precipitation throughout the state of California, the likelihood of a large fire increases in northern Cali fornia (especially in the Sierra)
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From page 179... ...
This reflects the fundamental differences in the climate impacts on fire regime in these regions due to differences in vegetation type. The change in the probability of the wildfire area burned in the western United States due to increased greenhouse gases can be estimated using the methods outlined in Littell et al.
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From page 180... ...
180 CLIMATE STABILIZATION TARGETS FIGURE 5.8 Map of changes in area burned for a 1ºC increase in global average tem perature, shown as the percentage change relative to the median annual area burned during 1950-2003. Results are aggregated to ecoprovinces (Bailey, 1995)
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From page 181... ...
Aggregating all 14 ecoprovinces in which fire is most sensitive to temperature variations, the net area burned by the median fire increases from 572,000 ha for the reference period 1970-2003, to 1,800,000 ha with a 1ºC global average temperature increase. Other investigators using different climate models and a variety also find thata climate change will increase the risk of wildfire throughout the western United States, so long as fuel is not limiting.
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From page 182... ...
. Changing risk of heat waves and droughts, storms and floods, and rising sea levels are just a few of the hazards climate change poses to infrastructure (Kraas, 2008)
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From page 183... ...
Impacts from coastal erosion and flooding can be driven by sea level rise and storm surge as well as by land-use decisions and other processes characteristic of, and which can
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From page 184... ...
Petersburg, Russia; and multiple devices now being installed to protect Venice at the border of its lagoon and the Adriatic Sea. The city is considering adjust FIGURE 5.10 Projected return time of coastal storms relative to future sea level rise for 5-10.eps New York City (Based on Kirshen et al., 2008a)
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From page 185... ...
The magnitude of impacts from sea level rise and storm surge breaching of the levees currently protecting the region is estimated at tens of billions of dollars over the next few decades alone (CALFED, 2009)
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From page 186... ...
186 CLIMATE STABILIZATION TARGETS FIGURE 5.12 Infrastructure at risk from sea level rise, storm surge, and levee failure in the Sacramento-San Joaquin Delta includes highways, roads, and rail lines; gas and oil production fields and pipelines; and homes and farms. Source: CALFED (2009)
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From page 187... ...
. Although warmer winter temperatures are expected to reduce demand for heating energy, observed correlations between daily mean near-surface air temperature and electricity demand suggest that warmer summer temperatures and more frequent, severe, and prolonged extreme heat events will likely increase demand for cooling energy, particularly as use of air conditioning increases around the world (see Figure 5.14)
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From page 188... ...
. The reliability of energy supplies can be affected by the frequency of droughts and accompanying heat waves, which increase the temperature of the cooling water beyond what the plant may be permitted to release.
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From page 189... ...
The relationship between hydropower generation and precipitation tends to be proportional, with a 1% change in precipitation resulting in approximately 1% change in power generation. However, projecting future climate effects on hydropower generation is limited by uncertainties in precipitation projections.
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From page 190... ...
four U.S. cities by global temperature change, and for (b)
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From page 191... ...
. In the future, extreme heat days and heat wave frequency, intensity, and duration is projected to increase with global mean temperature, while the frequency and intensity of winter cold is projected to decrease (Tebaldi et al., 2006; IPCC, 2007a)
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From page 192... ...
average for that same calendar day. Projected changes are for5-15 periods during which mean global mean Figure 20-year temperature increased by 1°C, 2°C, and 3.5°C, respectively relative to the 1961-1979 average.
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From page 193... ...
Under a 2°C change in global mean temperature, annual average mortality rates are projected to equal those of 1995. Under a 4°C change in global mean temperature, annual average mortality is projected to be twice 1995 levels, with 1995-like heat waves occurring as frequently as three times per year (Hayhoe et al., 2010)
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From page 194... ...
Long-Term Impacts of Heat Stress Many of the impact studies summarized in this section and elsewhere throughout this report focus on future projections for the next few decades; nearly all of the impact studies in the literature, regardless of focus area, con fine estimates of potential impacts to this century. This limits quantification of impacts based on GCM simulations driven by the SRES scenarios to those associated to global mean temperature changes of 4°C or less, depending on the GCMs and scenarios used to generate future projections.
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From page 195... ...
, subsequent studies have highlighted how the complexity of the systems -- involving viral, bacterial, plant, and animal physiology, as well as sensitivity to changes in climate extremes, including precipitation intensity and temperature variability -- challenges attempts to resolve the influence of historical climate change on observed trends in disease incidence and develop future projections specific to any particular level of global temperature change. This is even true for what many previously considered the poster child for the influence of climate change on infectious diseases, the spread of malaria throughout the East African highlands (e.g., Pascual et al., 2006)
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From page 196... ...
. Current and future deficiencies in watershed protection, infrastruc ture, and storm drainage systems will likely increase the risk of contamina tion events as climate variability increases (Rose et al., 2000)
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From page 197... ...
. The geographic range of any species includes only areas where individuals can endure the extreme temperature and water stress occurring at those locations (Gordon,1982; Chown and Gaston, 1999)
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From page 198... ...
. The increase in global average temperatures over that time period was ~0.4°C, although changes in land temperatures, especially at higher latitudes, were some factor of two larger (IPCC, 2007a)
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From page 199... ...
IMPACTS IN THE NEXT FEW DECADES AND COMING CENTURIES 199 Contrary to what has been found for spring phenology, trends in autumn phenologies are not as clear. In the spring, animals are getting ready to breed and are driven to breed as earlier as possible.
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From page 200... ...
. Species most affected by reductions in Arctic sea-ice extent are those with limited distributions and specialized feeding habits that depend on ice for foraging, reproduction, and predator avoidance, including the ivory gull (Pagophila eburnean)
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From page 201... ...
These include the size of the species population (large population size is much more stable than a small size) ; the size of the range of the species (a species with a larger range size is less likely to become rare and then extinct)
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From page 202... ...
These species are called functionally extinct. When that assistance is not possible, there is still a time lag due to humans not being comfortable declaring a species extinct.
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From page 203... ...
is also as important as FIGURE 5.17 Map showing the distance to potential cool refuges, where cool is defined as the temperatures 5-17.eps in 2100 are equal to or cooler than the temperatures in the 1960s. Used 0.5 x 0.5 latitude-longitude blocks.
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From page 204... ...
Species that are in trouble unless aided by humans are called functionally extinct. Examples of functionally extinct species are those that are on oceanic islands or mainland islands, such as oasis within a desert, because unless they fly, dispersing to a cooler refuge is not possible.
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From page 205... ...
. On both panels the red line is the model output.
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From page 206... ...
, ocean acidification via altered seawater chemistry from rising atmospheric CO2 (Section 4.9) , and sea-level rise via coastal habitat loss.
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From page 207... ...
. Numerical models project declining low-latitude marine primary production in response to 21st century climate warming (Sarmiento et al., 2004; Steinacher et al., 2010)
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From page 208... ...
The magnitude of the primary production changes are shown in percent normalized to global mean areal primary production rate and are presented for a nominal increase in global mean surface air temperature of 1°C. Source: Steinacher et al.
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From page 209... ...
. Models project longterm reductions of 1-7% in the global oxygen inventory and expansions of open-ocean oxygen minimum zone over the 21st century (Frölicher et al., 2009; Keeling et al., 2010)
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From page 210... ...
, and CO2 fertilization of zooxanthella does not alleviate acidification effects. Studies of net community calcification rates for coral reef ecosystems indicate that overall net calcification also decreases with rising CO2 (Silverman et al., 2007)
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From page 211... ...
Warming and more local human impacts have been associated with declines in the health of coral reef ecosystems worldwide. Bleaching can occur for sea surface temperature changes as small as +1-2°C above climatological maximal summer sea surface temperatures, and more frequent and intense bleaching events are anticipated with further climate warming (e.g., Veron et al., 2009)
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From page 212... ...
Yet perhaps because of the complex nature of national security threats and the paucity of relevant data, there are relatively few quantitative exam ples that document the climate sensitivity of phenomena related to national security. Some empirical evidence suggests an important role for climate in domestic and international conflict.
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From page 213... ...
Here we present two examples of areas where information on the next few centuries is available. Circulation About half of the AR4 climate models were used to project the future climate beyond 2100 to 2200.
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From page 214... ...
Too few of the higher end AR4 climate models have been integrated far enough into the future to assess whether persistently high greenhouse gas concentrations will cause a permanent change to the strength of the MOC. Sea Ice Beyond 2100 Climate model simulations suggest that in the decades following 2100 the Arctic may be perennially ice-free (Winton, 2006a,b; Eisenman and Wettlaufer, 2009)
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From page 215... ...
The increased melt will contribute to sea level rise. Sea ice in the Arctic is of major ecological importance; it is a habitat for a variety of species.
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