Pinpointing Climate Change
Pinpointing Climate Change
Pinpointing Climate Change
By Audrey Resutek and Erwan Monier, MIT Joint Program on the Science and Policy of Global Change
How severely will climate change affect different regions universally agreed on amount of climate change that
the United States? It depends on climate policy, says will take place.
new research by the MIT Joint Program on the Science
and Policy of Global Change. In fact, estimates that point to a single number for
changes in temperatures and precipitation may be
The US National Climate Assessment, released this misleading, precisely because they do not capture this
spring by the White House, describes a troubling array uncertainty. It is more useful to think of estimates of
of climate woes, from intense droughts and heat waves future climate change as a range of possible effects.
to more extreme precipitation and floods, all caused by The range of potential warming, for example, follows a
climate change. The report also describes how climate bell curve, with the most likely change in temperature
change is expected to impact regions across the United falling at the highest point of the curve. The farther you
States in the future, yet it notes that exact regional travel from the curve’s peak, toward the tails, the more
forecasts are difficult to pin down. At the larger scale, unlikely the temperature change. While the extreme
it is clear that climate is changing, but local predictions temperature increases at the curve’s tails are unlikely,
can disagree on the extent to which temperatures will they still fall within the realm of possibility, and are
increase, and what regions will be hit the hardest by worth considering because they represent-worst case
precipitation changes. scenarios.
Researchers at the MIT Joint Program on the Science The biggest source of uncertainty
and Policy of Global Change examined four major fac-
tors that contribute to wide-ranging estimates of future The MIT study1, published this spring in a special edition
regional climate change in the United States, with an of Climatic Change, looked at how different sources of
eye toward understanding which factors introduced the uncertainty affect estimates of future regional climate
most uncertainty into simulations of future climate. They change in the United States – in other words, how do dif-
find that the biggest source of uncertainty in climate ferent factors affect the width of the range of estimates?
modelling is also the only one that humans have control The study concludes that lack of information about future
over – policies that limit greenhouse gas emissions. climate policy is the biggest source of uncertainty over
the next century for simulations of both temperature
In this context, the term “uncertainty” does not mean and precipitation change. Climate policy introduces
that there is a lack of scientific consensus that climate uncertainty into the mix when researchers must try to
is changing. Instead, uncertainty refers to the fact that predict what regulations will affect emissions in the
using different assumptions for the variables that go into future, leading to varying levels of global greenhouse
a climate model – for example, the amount of greenhouse gas emissions.
gases emitted over the next century, or how sensitive
the climate is to changes in carbon dioxide levels – will
produce a range of estimates. Overall, these estimates
indicate that the Earth will be a warmer and wetter 1
Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A
place over the coming century, but there is no single framework for modeling uncertainty in regional climate change. Climatic
Change, online first, doi: 10.1007/s10584-014-1112-5.
Cities – particularly megacities – are becoming focal Understanding the dynamics between migration and
points for climate change impacts. Rapid urbanization, cities is an important priority of the International Orga-
accelerating demand for housing, resource supplies and nization for Migration (IOM). The Organization´s 2014
social and health services, place pressure on already World Migration Report and upcoming Ministerial-level
stretched physical, social and regulatory infrastructure, conference will be devoted to migrants and cities.3 This
heightening risks and vulnerability. In South America, article highlights some of the recent processes linking
internal migration flows – as well as immigration – are population mobility, urban settlements and environmen-
mostly to cities. Migrants, notably those of low socio- tal change, including climate change in South America.
economic status, are often particularly vulnerable as they
are more likely to reside in areas at risk of environmental Cities and urban growth in South America
hazards. They are also likely to lack local knowledge,
networks and assets, and are, therefore, less prepared South America and the Caribbean is the most urbanized
to cope with, and avoid, the impacts of these hazards.1 of the developing regions and one of the most urbanized
in the world. In 2010, 83% of the population of South
The impact of climate change and environmental deg- America resided in cities – it will be 86% by 2020. While
radation on migration and cities is not fully known. Sea the Southern cone has some of the lowest population
level rise, land degradation and desertification, as well densities in the world, a high proportion live in one or
as changes in water availability, including glacial melt, two very large cities per country.
are three important factors in the interplay of migration
drivers and environmental change. Additional migration More than 20% of the population of Latin America is
to cities is likely to exacerbate pre-existing vulnerabilities concentrated in the largest city of each country. With
related to inequality, poverty, indigence and informality total populations in excess of 10 million, Buenos Aires,
(informal work and settlements), and worsen the situa- Rio de Janeiro, Sao Paulo, and Belo Horizonte already
tion of those exposed to environmental risk factors. This count as megacities. While Bogota, Lima and Santiago
places further stress on the ability of cities to adapt to are approaching the 10 million mark. These cities make
climate change. At the same time, migration and other up social, economic and, in many cases, political hubs,
forms of mobility are common responses for coping being home to a major share of urban dwellers in the
with and adapting to environmental hardship, stress region.
and risks. Migrants make important contributions to the
cities that they live in, and migration to cities should, In the last decades, urban growth within South America
therefore, be appropriately managed and planned for.2 has been less rapid in large cities and megacities than
1
Senior Regional Specialist in Migration and Development for South Actions for the Climate-Induced Migration, Hamburg, 16-18 July 2013
America, International Organization for Migration (IOM) ciesin.columbia.edu/binaries/web/global/news/2013/adamo_hamburg-
2
Associate Research Scientist at CIESIN (Center for International earth conf_jul2013.pdf. Ms Adamo is also a member of ALAP (Latin American
Science Information Network), Co-coordinator of PERN (Population- Association for Population). In 2015 IOM and ALAP will organize a joint
Environment Research Network) and Adjunct Assistant Professor at workshop for academics on Migration, Environment, Climate Change
Columbia University. This article draws on her presentation “Migration, and Development.
cities and climate change in Latin America” for the Hamburg Conference 3
Forthcoming in 2014.
The increase and intensity of sudden onset natural hazards Additionally, a large proportion of urban expansion is
such as droughts, extreme temperatures and heavy rains taking place in areas exposed to environmental hazards
are likely to be the most immediate impacts of climate such as low-lying deltas and, low-lying plains, coastal
change on cities, linked with mobility. The urban popula- zones, stepped slopes and drylands. There is an increas-
tion in South America is concentrated in areas of high ing concentration of population on potentially hazardous
vulnerability to environmental and climate hazards. Cities locations in coastal megacities, especially in informal settle-
located in areas at high risks of droughts, earthquakes and ments. These areas are ill-suited to settlements as they are
particularly prone to flooding and seasonal storms, and
risks are amplified due to lack of essential infrastructure
5
Hoffmann, D. (2008) Consecuencias del Retroceso Glaciar En La and services or inadequate provision for adaptation. For
Cordillera Boliviana. Pirineos, 163, 77-84 example, in Buenos Aires, informal settlements can be