Abrupt Climate Change Inevitable Surprises (2002) / Chapter Skim
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5 Economic and Ecological Impacts of Abrupt Climate Change
5 Economic and Ecological Impacts of Abrupt Climate Change
Pages 118-152
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From page 118... ...
In particular, many recent paleostudies indicate that current climate is much more stable than were climates in earlier periods. One notable aspect of large, abrupt global and regional climatic changes is precipitation, which is inherently more variable than temperature.
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From page 119... ...
While the discussion of future climate changes has been dominated by the paradigm of gradual climate warming, we highlight the paleoclimate evidence of Holocene drought because such abrupt changes are likely to be more disruptive of human societies, especially in those parts of the globe that currently have water shortages and marginal rain-fed agriculture. The recognition of abrupt changes in past climates reinforces concerns about the potential for significant impacts of anthropogenic climate change.
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From page 120... ...
The workshop highlighted a considerable body of work directly relevant to understanding impacts of abrupt climate change exists in disciplines such as archaeology, sociology, and geography, and identified opportunities for the concept of abrupt climate change to motivate better connections between these diverse fields of study. RECENT SCIENTIFIC STUDIES IN THE ECOLOGICAL AND SOCIAL SCIENCES Given the focus of this chapter, it is important to understand the term "abrupt climate change" in the context of ecological and economic systems.
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From page 121... ...
. Abrupt impacts therefore have the potential to occur when gradual climatic changes push societies or ecosystems across thresholds and lead to profound and potentially irreversible impacts, just as slow geophysical forcing can cross a threshold and trigger an abrupt climate change.
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From page 122... ...
However, if climate is changing, or if the underlying climate system is itself variable, decisions based on past precipitation, runoff, and flood patterns are likely to build in thresholds that incorrectly estimate potential threats compared to decisions based on expectations that allow for changes in climatic means or climate variability. (For more information on the flooding and response in Grand Forks and along the Red River, see International Red River Basin Task Force, 2000.)
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From page 123... ...
The variability is measured as the deviations from trend of real gross output originating in agriculture in 1996 prices over the 1929-2000 period (Figure 5.2 and is caused by a wide variety of factors including weather, floods, exchange-rate changes, demand volatility, as well as bad harvests abroad. The year-to-year variability of agricultural output has risen over time along with the growth in iReal gross product output above originating in agriculture is the value added in the agricultural sector, which equals total output less purchases (such as fuel)
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From page 124... ...
Surprisingly, however, the vulnerability of the overall economy to agricultural shocks has declined over the last seven decades. The overall vulnerability is here measured as the ratio of the deviation from trend of real gross output shown in Figure 5.2 divided by trend real gross domestic product (Figure 5.3~.
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From page 125... ...
:~\~ o -.8 — 1940 1 960 Year 1 980 2000 FIGURE 5.3 Relative variability of US farm output as share of total gross domestic product, 1929-2000. Relative variability is the dollar variability shown in Figure 5.2 as a percent of trend real gross domestic product.
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From page 126... ...
Total economic losses from hurricanes in the United States have increased sharply during this period; however, after accounting for inflation, wealth, and population, no clear trend emerges, as shown in Figure 5.5. (SOURCE: Pielke and Landsea, 1998.)
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From page 127... ...
Impact of Abrupt Climate Change on Economic and Ecological Stocks One way of understanding the impact of abrupt climate change is through its impact on economic and ecological stocks or "capital stocks." This approach rests on the idea that most useful economic and ecological activity depends on stocks of capital, where that phrase is defined in the most general sense as accumulations of valuable and durable, tangible and intangible goods and services.3 In the economy, capital stocks include tangible goods such as factories, equipment, and roads as well as intangible items such as patents, intellectual property, and institutions. Similarly, ecosystems depend on stocks of species, forests, water, and carbon as well as complex "webs" of interacting systems.
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From page 128... ...
It is generally believed that gradual climate change would allow much of the economic capital stocks to roll over without major disruption. By contrast, a significant fraction of these stocks probably would be rendered obsolete if there were abrupt and unanticipated climate change.
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From page 129... ...
The vulnerability of capital stocks to climate change (measured as the percent of the value destroyed by an abrupt event) is a function of the warning time and the lifetime of the capital stock (Figure 5.6~.4 Suppose, for example, that the owner of capital stock has warning that an abrupt event will occur and it will render the capital completely obsolete.
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From page 130... ...
., 20 40 60 Warning time (years) 80 1 00 FIGURE 5.6 Vulnerability of capital stocks is higher with reduced warning times and longer lifetimes.
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From page 131... ...
Is Abrupt Climate Change Likely to Exacerbate the Effects of Gradual Climate Change? Until recently, most research on the impacts of climate change has focused on gradual climate change primarily because the early scenarios developed by climate scientists asked questions such as "what would happen if CO2 doubled?
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From page 132... ...
The major reason for this difference, as discussed previously, is that economies and ecological systems usually will have an easier time adapting to more gradual and better anticipated changes. The net effect of small gradual climatic changes on the economy, as is indicated by most current economic studies for developed countries, is likely to be small relative to the overall economy (Figure 5.7~.
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From page 133... ...
On the other hand, many manufacturing processes are thought to be relatively robust to climate change at any temporal scale. For natural systems, it is well documented that gradual climate change can affect species distribution, population abundance, morphology, and behavior, ultimately affecting community structure (Easterling et al., 2000~.
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From page 134... ...
demonstrate how rapidly boreal forest can be replaced by mixed hardwoods, as was observed in eastern United States ecotonal forests at the close of the Younger Dryas. European pollen records from the cold event about 8,200 years ago indicate significant species changes in fewer than 20 years (Tinner and Lotter, 2001~.
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From page 135... ...
where ponderosa pine experienced high mortality rates in less than 5 years and the ecotone migrated over 2 km. Woody mortality loss occurs much faster than tree growth gain, which has pervasive and persistent ecological effects on associated plant and animal communities.
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From page 136... ...
But recent research suggests that the rate of species extinctions is on the order of 100 to 1,000 times higher than before humans were dominant (Lawson and May, 1995; Vitousek et al., 1997~. For example,
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From page 137... ...
. crease In species extinctions Is In part because extinctions are occurring on the time scale of human economies, but evolution typically occurs more slowly (except for microorganisms, including those that cause disease)
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From page 138... ...
138 ABRUPT CLIMATE CHANGE Human Population Size 1 Resource Use Economic Activity Agriculture Industry Recreation International Commerce 1 | Land Transformation | | Biotic Additions and Losses Land Clearing ~ ~ Invasion Forestry . Hunting Grazing ~ ~ ~ Global ~ ~ Fishing Intensification Biogeochemistry Carbon Nitrogen Water Synthetic Chemicals Other Elements ~ l ~ ~ ~ ~ Climate Change Loss of Biological Diversity Enhanced Greenhouse Effects Extinction of Species and ~ ~ Populations Aerosols Loss of Ecosystems Land Cover FIGURE 5.8 The many direct and indirect impacts of humanity on the earth's natural ecosystems is shown, with links between climate change, enhanced greenhouse gases, and biological diversity (modified from Vitousek et al., 1997~.
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From page 139... ...
Ice sheets are linked to abrupt climate change because melting of Greenland or the West Antarctic ice sheet would add directly to global sea level rise and to possible changes in the thermohaline circulation (Manatee and Stouffer, 1997~. Much attention has been focused on the possibility of a rapid collapse of the West Antarctic ice sheet.
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From page 140... ...
Laser-altimeter surveys in the 1990s indicated an overall negative mass balance for Greenland ice that results in a 0.13 mm per year sea level rise (Krabill et al., 2000~. Since the late 1800s the margin of the Greenland ice sheet has retreated 2 km in some places (Funder and Weidick' 1991)
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From page 141... ...
Perhaps the most important is agriculture, which is the sector most heavily affected by weather and climate. Current studies indicate that the impact of gradual climate change on agriculture over the next few decades is likely to be relatively modest for the United States.
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From page 142... ...
Forests A second priority sector for research is forests. This sector may be affected more than agriculture by abrupt climate change because forests are highly climate-sensitive, with long-lived ecological and economic capital stocks.
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From page 143... ...
~ ~ . ~ ~ o -100 143 o Global Mean Surface 7bmperatum Change, degrees (; FIGURE 5.9 Illustration of the impacts of gradual climate change with adaptation and abrupt climate change without adaptation (Reilly, submitted)
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From page 144... ...
The impact of climate change on forest systems is currently an area of intensive research (e.g., Hansen et al., 2001a; Shafer et al., 2001) , although the focus is on gradual climate change.
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From page 145... ...
Changes in the Great Lakes water levels have also been linked to climate change, most recently in the last few decades (Sellinger and Quinn, 1999~. The declining extent of the Aral Sea and Lake Chad involve both human impact and climate change (Kling, 2001~.
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From page 146... ...
As soil dries, microbes limited by water respire less soil organic matter, which produces less carbon dioxide and methane. As soil moisture increases, respiration increases and more greenhouse gases are produced.
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From page 147... ...
Recent extreme weather events have precipitated a number of disease outbreaks (Epstein, 1998~. Criteria that define emerging infectious diseases of humans were recently used to also identify a range of emerging infectious diseases that affect wildlife (Daszak et al., 2000~.
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From page 148... ...
It is useful to remind ourselves that over the longer term, technological changes can modify the impact of climate and of abrupt climate change on human activities, on ecosystems, and on economic welfare. Irrigation and fertilization change the impact of climate on agriculture; plant and animal breeding have produced drought- and pest-resistant varieties; forest management practices have changed the pattern of tree growth and timber harvesting; land fills, dikes, and sea walls have kept the sea at bay in low-lying regions; dams and drip irrigation have spread out available water supplies; heat pumps and white roofs can change local energy balances; social and private insurance have reduced individual vulnerability to extreme weather events; vaccines and medications have reduced the impact of many diseases
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From page 149... ...
Over the last decade, these models have been deployed to help understand the potential impacts of climate change on economic and ecological systems. As a result, substantial advances have been made in understanding the way that economic and ecological systems may be affected by gradual climate change.
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From page 150... ...
Low abatement rates occur early and for low THCC costs, while high abatement rates occur in later periods and for high THCC costs. Two features of the result are worth noting.
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From page 151... ...
The efficient carbon abatement policies are derived in an "optimal economic growth model." The figure shows abatement rate contours (reduction rate as a percent of baseline) as a function of time on the horizontal axis and damages from a shutdown of the thermohaline circulation as a percent of world output on the vertical axis.
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From page 152... ...
(2000~. This study examined outputs of general circulation models that show changes in extreme events for future climates under greenhouse warming scenarios, such as increases in high temperatures, decreases in extreme low temperatures, and increases in precipitation events.
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