TODAY’S ENVIRONMENTAL ISSUES 4
represent more than half the difference in temperatures between the last ice age
and today (Henson 2014, 6). The IPCC’s Fifth Assessment Report states that “cli-
mate change will amplify existing risks and create new risks for natural and human
systems. Risks are unevenly distributed and are generally greater for disadvantaged
people and communities in countries at all levels of development” (IPCC Core
Writing Team 2014, 13). These risks include displacement of populations along
coastal regions, increased food insecurity, heightened competition for scarce fresh-
water, and increased vulnerability to heat waves and other extreme weather events.
In a study of climate change’s effects on human mortality, the World Health
Organization found an additional 241,000 deaths from heat exposure, malaria,
diarrhea, and childhood malnutrition are likely by the year 2030 due to degraded
environmental conditions (Hales et al. 2014). Those figures do not account for
declining economic conditions or for rising military conflicts, both of which are
serious concerns associated with climate change.
Declining economic conditions may be very significant: one recent study cal-
culated that if warming is not mitigated, by the year 2100 humans would see a 23
percent loss in average global incomes, accompanied by greatly increasing inequal-
ities (Burke, Hsiang, and Miguel 2015). This study does not factor economic costs
associated with sea level rise. A recent paper that focuses on economic costs of sea
level rise (using the IPCC estimates of 0.3 m to 1.24 m of rise) calculates those
costs to be somewhere between 0.3 percent and 9.3 percent of global gross domes-
tic product, depending on amount of sea level rise and socioeconomic responses
over time (Hinkel et al. 2014).
Rising military conflicts may also be significant, as emphasized by a 2015 U.S.
Department of Defense report to Congress. The report identifies security risks from
military conflicts driven by social instability, economic stress, and population dis-
placement resulting from flooding, drought, and higher temperatures. It also pre-
dicts greater demand on military resources for humanitarian responses to extreme
weather events and increased activity in the Arctic as that region warms up. The
report makes clear that the Defense Department’s judgment is that climate is a
“present security threat, not strictly in the long-term”—and that “although climate-
related stress will disproportionately affect fragile and conflict-affected states, even
resilient, well-developed countries are subject to the effects of climate change in
significant and consequential ways” (U.S. Department of Defense 2015).
Aside from the impacts on human health and welfare, climate change is alter-
ing ecosystems in ways that are increasing extinction risks for nonhuman species.
One recent study of more than 130 published research articles projected extinction
rates at various levels of temperature rise. If global temperature rise is limited to the
agreed-upon target of 2ºC (increasingly considered unlikely by most experts), an
extinction rate of 5.2 percent of current species is expected. At an increase of 3ºC,
the extinction rate rises to 8.5 percent. The “business as usual” scenario results in
a temperature increase of 4.3ºC and the extinction of 16 percent, or nearly 1 in 6
species alive today (Urban 2015, 571–573).
