Transcript Introduction

Introduction
Global Environmental Change –
Lecture 1 Spring 2017
Why Global Environmental Change?
• This course was designed as a climate change
course, yet the name chosen was Global
Environmental Change – WHY?
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Speculation
• People have speculated that human activities
might influence the environment
• The Greeks, and later others, thought that
forest cutting might influence rainfall, but
there were disagreements about whether the
influence would be positive (more rainfall) or
negative
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Ice Ages
• When it was discovered that the earth had once been covered
with ice, the obvious questions concerned the cause
• Possible causes:
 Variations in the heat of the Sun?
 Volcanoes erupting clouds of smoke?
 The raising and lowering of mountain ranges, which diverted wind
patterns and ocean currents?
 Changes in the composition of the air itself?
 Or?
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Man’s Effects
• In 1827, Jean Baptiste Joseph Fourier, a French
mathematician, suggested that gases in the earth’s atmosphere
might absorb infrared radiation and influence earth’s climate
• He made an analogy to a greenhouse, although the name
greenhouse effect came much later
• In 1896, Swedish scientist Svante August Arrhenius published
a paper in which he calculated the effect of carbon dioxide in
heating the earth – more about this later
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Callendar Effect
• By the 1930s, it was discovered that the United States
and North Atlantic region had warmed significantly
during the previous half-century
• Guy Stewart Callendar (1898 - 1964), an English steam
engineer and inventor, developed a theory that linked
rising carbon dioxide concentrations in the atmosphere
to global temperature
• Although previously discussed by Fourier, Arrhenius,
and others, the effect is sometimes called the Callendar
effect, because Callendar insisted that warming was on
its way
G.S. Callendar, 1934
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Scientific Investigation
• Callendar’s claims did provoke scientific
investigation
• At the suggestion of Roger Revelle, Charles David
Keeling began measuring carbon dioxide and, later,
other greenhouse gas concentrations in the
atmosphere, starting in 1957
• It was quickly discovered that CO2 levels were
increasing
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The Real Reason
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Credit
• Much of the remainder of this lecture is based on
Discovery of Global Warming site created by Spencer
Weart, with initial support from the American
Institute of Physics, the National Science Foundation
and the Alfred P. Sloan Foundation
• http://www.aip.org/history/climate/impacts.htm#impa
cts
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Scientific Progress
• Simple mathematical models of the climate were developed
 Feedbacks that could make the system surprisingly variable were
discovered
• Ingenious ways to retrieve past temperatures by studying
ancient pollens and fossil shells were developed
 Apparently, grave climate change could happen, and in the past had
happened, within as little as a few centuries
 Computer models of the general circulation of the atmosphere,
the fruit of a long effort to learn how to predict (and perhaps
even deliberately change) the weather, reinforced this finding 10
1960’s
• Calculations. made in the late 1960’s, suggested average
temperatures would rise a few degrees within the next century
• Groups of scientists that reviewed the calculations
 They were thought to be plausible
 No need for any policy action, aside from putting more effort into
research to find out for sure what was happening , was regarded as
necessary, since the next century was a long way off
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1970’s
• The rise of environmentalism raised public doubts about the
effects of human activity on the planet
• Curiosity about climate turned into anxious concern
 Greenhouse effect concerns
 Some scientists pointed out that human activity was putting dust and
smog particles into the atmosphere, where they could block sunlight
and cool the world
 Analysis of Northern Hemisphere weather statistics showed that a
cooling trend had begun in the 1940s and was continuing
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Confusion
• The mass media were confused
 Sometimes predictions of a balmy globe, with coastal areas flooded as
the ice caps melted, were given
 Sometimes the media warned of the prospect of a catastrophic new ice
age
• Study panels, first in the U.S. and then elsewhere, began to
warn that one or another kind of future climate change might
pose a severe threat
 Scientific agreement was limited to saying scientists scarcely
understood the climate system, and much more research was needed
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Increasing Research Activity
• Research activity did accelerate, including huge data-gathering
schemes that mobilized international fleets of oceanographic
ships and orbiting satellites
• Scientists were coming to understand that climate is an intricate
system responding to a great many influences
 Volcanic eruptions and solar variations were still plausible causes of
change, with some arguments that these would swamp any effects of
human activities
 Even subtle changes in the Earth's orbit could make a difference
 To the surprise of many, studies of ancient climates showed that astronomical cycles had
partly set the timing of the ice ages
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Chaos
• The climate appeared to be so delicately balanced that almost
any small perturbation might set off a great shift
 According to the new "chaos" theories, in such a system a shift might
even come all by itself , and very suddenly
 Support for the idea came from ice cores arduously drilled from the
Greenland ice sheet, which showed large and disconcertingly abrupt
temperature jumps in the past
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Late 1970’s
• Global temperatures began to rise again
 Many climate scientists had become convinced that the rise was likely
to continue as greenhouse gases accumulated
 One unexpected discovery was that the level of certain other gases was
rising, which would add seriously to global warming
 Some of these gases also degraded the atmosphere's protective ozone
layer, and the news inflamed public worries about the fragility of the
atmosphere
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1980’s
• Greatly improved computer models began to suggest how dramatic climate
jumps could happen, for example, through a change in the circulation of
ocean currents
• Experts predicted:
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Droughts
Storms
Rising sea levels
Other disasters
 Politicians began to suspect there might be a public issue here
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Beginnings of the Model Controversies
• Modelers had to make many arbitrary assumptions about clouds and the
like, and reputable scientists disputed the reliability of the results
• Others pointed out how little was known about the way living ecosystems
interact with climate and the atmosphere
 For example, what were the effects of agriculture and deforestation in adding
or subtracting carbon dioxide from the air
• One thing the scientists agreed on was the need for a more coherent
research program
• By around 2000, some predicted, an unprecedented global warming would
become apparent
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1988
• In the summer of 1988, climate scientist's worries first caught
wide public attention
• The summer of 1988 was the hottest on record till then
• An international meeting of scientists warned that the world
should take active steps to cut greenhouse gas emissions
• James Hansen spoke out, becoming a powerful voice urging
both climate research and efforts to reduce carbon dioxide
emissions
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Beginnings of Climate Wars
• Corporations and individuals who opposed all government
regulation began to spend many millions of dollars on
lobbying, advertising, and "reports" that mimicked scientific
publications, in an effort to convince people that there was no
problem at all
• Environmental groups, less wealthy but more enthusiastic,
helped politicize the issue with urgent cries of alarm
• Many scientific uncertainties, and the sheer complexity of
climate, made room for limitless debate over what actions, if
any, governments should take
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Early 1990’s
• Was the global temperature rise due to an increase in the Sun’s
activity?
 Solar activity began to decline, but the temperature soared faster than ever
• Did computer models reproduce the present climate only because
they were tweaked until they matched it, making them worthless
for calculating a future climate change?
 Improved models successfully predicted the temporary cooling due to a
huge volcanic explosion in 1991 and passed many other tests
 In particular, the modelers could now reproduce in detail the pattern of
warming, changes in rainfall, etc. actually observed in different regions of
the world over the past century (hindcasting)
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State of the Climate Models
• Modeling teams that made different assumptions
about the physics of clouds and pollution got
somewhat different results
 Most of them found a warming of around 3°C when the
carbon dioxide level doubled, late in the 21st century
 Some found a rise of 2°C or perhaps a bit less, costly but
probably manageable
 Others calculated a 5°C rise or even more, an unparalleled
catastrophe
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Antarctic Ice Cores
• For hundreds of thousands of years, carbon dioxide and
temperature had been linked: anything that caused one of the
pair to rise or fall had caused a rise or fall in the other
• It turned out that a doubling of carbon dioxide had always
gone along with a 3°C temperature rise, give or take a degree
or two
 This provided striking confirmation of the computer models, from
independent geologic evidence
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Response – Creation of IPCC
• “It was established by the United Nations Environment
Programme (UNEP) and the World Meteorological
Organization (WMO) in 1988 to provide the world with a clear
scientific view on the current state of knowledge in climate
change and its potential environmental and socio-economic
impacts
• In the same year, the UN General Assembly endorsed the
action by WMO and UNEP in jointly establishing the IPCC”
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What is IPCC?
• “The IPCC is a scientific body under the auspices of
the United Nations (UN)
• It reviews and assesses the most recent scientific,
technical and socio-economic information produced
worldwide relevant to the understanding of climate
change
• It does not conduct any research nor does it monitor
climate related data or parameters”
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IPCC Reports
• IPCC began to publish assessment reports:
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First Assessment Report (FAR) 1990
Second Assessment Report (SAR) 1995
Third Assessment Report (TAR) 2001
Assessment Report 4 (AR4) 2007
Assessment Report 5 (AR5) 2013
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IPCC Progress
• The world's governments had created a panel to give them the
most reliable possible advice, as negotiated among thousands
of climate experts and officials.
 By 2001, the Intergovernmental Panel on Climate Change (IPCC)
managed to establish a consensus, phrased so cautiously that scarcely
any expert or government representative dissented
 The IPCC announced that, although the climate system was so complex
that scientists would never reach complete certainty, it was much more
likely than not that our civilization faced severe global warming
 The discovery of global warming was essentially completed
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2000 – a New Millennium
• Scientists knew the most important things about how
the climate could change during the 21st century
• How the climate would actually change now
depended chiefly on what policies humanity would
choose for its greenhouse gas emissions
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2000’s
• Greatly improved computer models, together with an abundance of data of
many kinds, strengthened the conclusion that human emissions are very
likely to cause serious climate change
• The IPCC's conclusions were reviewed and endorsed by the national
science academies of every major nation from the United States to China,
along with leading scientific societies and indeed virtually every
organization that could speak for a scientific consensus
• Specialists meanwhile improved their understanding of some less probable
but more severe possibilities
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James Lawrence Powell Pie-Charts
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New Finding’s
• Dangerous change in ocean circulation seemed unlikely in the
next century or two
• There were signs that disintegrating ice sheets could raise sea
levels faster than most scientists had expected
• Worse, new evidence suggested that the warming was itself
starting to cause changes that would generate still more
warming
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Beginning of the 2010’s
• Scientists who had been predicting for decades that, by 2000,
the world would be significantly warmer were now obviously
correct
• Science reporters, business leaders, government advisers and
others increasingly believed them
• An ever larger number of individuals, corporate entities, and
government agencies at every level decided that something
had to be done
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Likely Consequences
• Likely consequences of restrained warming, by two
or three °C
 What we may expect if humanity manages to begin
restraining its emissions soon, so that greenhouse gases do
not rise beyond twice the pre-industrial level
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Anticipated Changes - 1
• Most places will continue to get warmer
 Especially at night and in winter
• Temperature change will benefit some regions while harming
others
 Patterns of tourism will shift
 Warmer winters will improve health and agriculture in some areas
 Globally, mortality will rise and food supplies will be endangered due to
more frequent and extreme summer heat waves and other effects
 Regions not directly harmed will suffer indirectly from higher food prices
and a press of refugees from afflicted regions
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Anticipated Changes - 2
• Sea levels will continue to rise for many centuries
 The last time the planet was 3°C warmer than now, the sea
level was at least 6 meters (20 feet) higher
 That submerged coastlines where many millions of people
now live, including cities from New York to Shanghai
 The rise will probably be so gradual that later generations
can simply abandon their parents' homes, but a ruinously
swift rise cannot be entirely ruled out
 Storm surges will cause emergencies
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Anticipated Changes - 3
• Weather patterns will keep changing
 Toward an intensified water cycle with stronger floods and droughts
 Most regions now subject to droughts will probably get drier (because of
warmth as well as less precipitation), and most wet regions will get wetter
 Extreme weather events will become more frequent and worse
• In particular, storms with more intense rainfall are liable to bring worse
floods
 Some places will get more snowstorms, but most mountain glaciers and
winter snowpack will shrink, jeopardizing important water supply systems
 Each of these things has already begun to happen in some regions
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Anticipated Changes - 4
• Ecosystems will be stressed
 Although some managed agricultural and forestry systems might
benefit in the first decades of warming
 Uncounted valuable species, especially in the Arctic, mountain areas,
and tropical seas, must shift their ranges
 Many that cannot will face extinction
 A variety of pests and tropical diseases are expected to spread to
warmed regions
 These problems have already been observed in numerous places
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Anticipated Changes - 5
• Increased carbon dioxide levels will affect biological
systems, independent of climate change
 Some crops will be fertilized, as will some invasive weeds (the balance
of benefit vs. harm is uncertain)
 The oceans will continue to become markedly more acidic, gravely
endangering coral reefs, and probably harming fisheries and other
marine life
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Anticipated Changes - 6
• There will be significant unforeseen impacts
 Most of these will probably be harmful, since human and natural
systems are well adapted to the present climate
 The climate system and ecosystems are complex and only partly
understood, so there is a chance that the impacts will not be as bad as
predicted
 There is a similar chance of impacts grievously worse than predicted
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Climate Denial
• Others insisted that the IPCC was wholly mistaken; there was
no need to worry
• A minority of scientists (scarcely any of them known for
contributions to climate science) who held to the old
conviction that human activity was too feeble to sway natural
systems
• Distrust of the climate experts was encouraged by corporations
and political interests that opposed any government
interference in the economy
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Representative Concentration Pathways
• Scenarios that include time series of emissions and
concentrations of the full suite of greenhouse gases (GHGs) and
aerosols and chemically active gases, as well as land use / land
cover
• The word representative signifies that each RCP provides only
one of many possible scenarios that would lead to the specific
radiative forcing characteristics
• The term pathway emphasizes that not only the long-term
concentration levels are of interest, but also the trajectory taken
over time to reach that outcome
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RCP 2.6
• One pathway where radiative forcing peaks at
approximately 3 W m–2 before 2100 and then declines
(the corresponding ECP assuming constant emissions
after 2100)
• Corresponds to concentrations of 450 ppm CO2eq
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RCP 4.5
• Intermediate stabilization pathways in which
radiative forcing is stabilized at approximately
4.5 W m–2 after 2100 (the corresponding ECPs
assuming constant concentrations after 2150)
• Corresponds to concentrations of 650 ppm
CO2eq
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RCP 6.0
• Intermediate stabilization pathways in which
radiative forcing is stabilized at approximately
6.0 W m–2 after 2100 (the corresponding ECPs
assuming constant concentrations after 2150)
• Corresponds to concentrations of 850 ppm
CO2eq
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RCP 8.5
• One high pathway for which radiative forcing reaches
greater than 8.5 W m–2 by 2100 and continues to rise
for some amount of time (the corresponding ECP
assuming constant emissions after 2100 and constant
concentrations after 2250)
• Corresponds to concentrations of 1370 ppm CO2eq
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Scenario Constraints
• Scenarios of how the future develops without
additional and explicit efforts to mitigate climate
change (‘baseline scenarios’) and with the
introduction of efforts to limit GHG emissions
(‘mitigation scenarios’), respectively, generally
include socio-economic projections in addition to
emission, concentration, and climate change
information
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AR5 Synthesis Report - 2014
• The Synthesis Report discussed four areas:
 SPM 1. Observed Changes and their Causes
 SPM 2. Future Climate Changes, Risks and Impacts
 SPM 3. Future Pathways for Adaptation, Mitigation and
Sustainable Development
 SPM 4. Adaptation and Mitigation
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Observed Changes and their Causes
• Human influence on the climate system is
clear, and recent anthropogenic emissions of
greenhouse gases are the highest in history
• Recent climate changes have had widespread
impacts on human and natural systems
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SPM 1.1
Observed changes in the climate system
• Warming of the climate system is unequivocal,
and since the 1950s, many of the observed
changes are unprecedented over decades to
millennia
• The atmosphere and ocean have warmed, the
amounts of snow and ice have diminished, and
sea level has risen
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1880-2015 Temperature Anomalies
• 2015 was the hottest year during this period
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2015 Temperature Percentiles
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SPM 1.2 Causes of climate change
• Anthropogenic greenhouse gas emissions have increased since
the pre-industrial era, driven largely by economic and
population growth, and are now higher than ever
• This has led to atmospheric concentrations of carbon dioxide,
methane and nitrous oxide that are unprecedented in at least
the last 800,000 years
• Their effects, together with those of other anthropogenic
drivers, have been detected throughout the climate system and
are extremely likely to have been the dominant cause of the
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observed warming since the mid-20th century
SPM 1.3 Impacts of climate change
• In recent decades, changes in climate have caused
impacts on natural and human systems on all
continents and across the oceans
• Impacts are due to observed climate change,
irrespective of its cause, indicating the sensitivity of
natural and human systems to changing climate
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SPM 1.4 Extreme events
• Changes in many extreme weather and climate events have
been observed since about 1950
• Some of these changes have been linked to human influences,
including a decrease in cold temperature extremes, an increase
in warm temperature extremes, an increase in extreme high sea
levels and an increase in the number of heavy precipitation
events in a number of regions
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Future Climate Changes, Risks and Impacts
• Continued emission of greenhouse gases will cause further
warming and long-lasting changes in all components of the
climate system, increasing the likelihood of severe, pervasive
and irreversible impacts for people and ecosystems
• Limiting climate change would require substantial and
sustained reductions in greenhouse gas emissions which,
together with adaptation, can limit climate change risks.
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SPM 2.1 Key drivers of future climate
• Cumulative emissions of CO2 largely determine
global mean surface warming by the late 21st century
and beyond
• Projections of greenhouse gas emissions vary over a
wide range, depending on both socioeconomic
development and climate policy
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SPM 2.2 Projected changes in the climate system
• Surface temperature is projected to rise over the 21st century
under all assessed emission scenarios
• It is very likely that heat waves will occur more often and last
longer, and that extreme precipitation events will become more
intense and frequent in many regions
• The ocean will continue to warm and acidify, and global mean
sea level to rise
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SPM 2.3 Future risks and impacts caused by a changing climate
• Climate 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
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SPM 2.4
Climate change beyond 2100, irreversibility and abrupt changes
• Many aspects of climate change and associated
impacts will continue for centuries, even if
anthropogenic emissions of greenhouse gases are
stopped
• The risks of abrupt or irreversible changes increase as
the magnitude of the warming increases
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Future Pathways for Adaptation, Mitigation
and Sustainable Development
• Adaptation and mitigation are complementary strategies for
reducing and managing the risks of climate change
• Substantial emissions reductions over the next few decades
can reduce climate risks in the 21st century and beyond,
increase prospects for effective adaptation, reduce the costs
and challenges of mitigation in the longer term, and contribute
to climate-resilient pathways for sustainable development.
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SPM 3.1
Foundations of decision-making about climate change
• Effective decision making to limit climate change and
its effects can be informed by a wide range of
analytical approaches for evaluating expected risks
and benefits, recognizing the importance of
governance, ethical dimensions, equity, value
judgments, economic assessments and diverse
perceptions and responses to risk and uncertainty
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SPM 3.2
Climate change risks reduced by mitigation and adaptation
• Without additional mitigation efforts beyond those in place
today, and even with adaptation, warming by the end of the
21st century will lead to high to very high risk of severe,
widespread, and irreversible impacts globally
• Mitigation involves some level of co-benefits and of risks due
to adverse side-effects, but these risks do not involve the same
possibility of severe, widespread, and irreversible impacts as
risks from climate change, increasing the benefits from nearterm mitigation efforts.
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SPM 3.3
Characteristics of adaptation pathways
• Adaptation can reduce the risks of climate change impacts, but
there are limits to its effectiveness, especially with greater
magnitudes and rates of climate change
• Taking a longer-term perspective, in the context of sustainable
development, increases the likelihood that more immediate
adaptation actions will also enhance future options and
preparedness
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SPM 3.4
Characteristics of mitigation pathways
• There are multiple mitigation pathways that are likely to limit warming
to below 2°C relative to preindustrial levels.
• These pathways would require substantial emissions reductions over the
next few decades and near zero emissions of CO2 and other long-lived
GHGs by the end of the century.
• Implementing such reductions poses substantial technological,
economic, social, and institutional challenges, which increase with
delays in additional mitigation and if key technologies are not available.
• Limiting warming to lower or higher levels involves similar challenges,
but on different timescales
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SPM 4. Adaptation and Mitigation
• Many adaptation and mitigation options can help address
climate change, but no single option is sufficient by itself
• Effective implementation depends on policies and cooperation
at all scales, and can be enhanced through integrated responses
that link adaptation and mitigation with other societal
objectives
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SPM 4.1
Common enabling factors and constraints for adaptation
and mitigation responses
• Adaptation and mitigation responses are underpinned by
common enabling factors
• These include effective institutions and governance,
innovation and investments in environmentally sound
technologies and infrastructure, sustainable livelihoods, and
behavioral and lifestyle choices.
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SPM 4.2 Response options for adaptation
• Adaptation options exist in all sectors, but their context for
implementation and potential to reduce climate-related risks
differs across sectors and regions
• Some adaptation responses involve significant co-benefits,
synergies and trade-offs
• Increasing climate change will increase challenges for many
adaptation options
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SPM 4.3 Response options for mitigation
• Mitigation options are available in every major sector
• Mitigation can be more cost-effective if using an
integrated approach that combines measures to reduce
energy use and the GHG intensity of end-use sectors,
decarbonize energy supply, reduce net emissions and
enhance carbon sinks in land-based sectors
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SPM 4.4
Policy approaches for adaptation and mitigation, technology and finance
• Effective adaptation and mitigation responses will depend on
policies and measures across multiple scales: international,
regional, national and sub-national
• Policies across all scales supporting technology development,
diffusion and transfer, as well as finance for responses to
climate change, can complement and enhance the effectiveness
of policies that directly promote adaptation and mitigation
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SPM 4.5
Trade-offs, synergies and interactions with sustainable development
• Climate change is a threat to sustainable development
• Nonetheless, there are many opportunities to link mitigation,
adaptation and the pursuit of other societal objectives through
• integrated responses (high confidence)
• Successful implementation relies on relevant tools, suitable
governance structures and enhanced capacity to respond
(medium confidence)
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What If?
• What if the CO2 level keeps rising to well beyond twice the
pre-industrial level along with a rise of other greenhouse
gases, as must inevitably happen if we do not take strong
action soon?
 The results will certainly be worse
• Under a "business as usual" scenario, recent calculations give
even odds that global temperature will rise 5°C or more by the
end of the century
 This will cause a radical reorganization and impoverishment of many
of the ecosystems that sustain our civilization
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What of the more distant future?
• If emissions continue to rise for a century, whether because we fail to rein
them in, or because we set off an unstoppable feedback loop in which the
warming itself causes ever more greenhouse gases to be evaporated into the
air, then the gases will reach a level that the Earth has not seen since tens of
millions of years ago
 The consequences will take several centuries to be fully realized, as the Earth
settles into its new state
 It is probable that, as in the distant geological eras with high CO2, sea levels
will be many tens of meters higher and the average global temperature will soar
far above the present value: a planet grossly unlike the one to which the human
species is adapted
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Answering the Original Question
• The foregoing discussion is intended as the answer to the
question posed at the beginning
• We are not just changing the climate, but we are engaged in a
planet-wide, severe, alteration of the environment
• For this reason, the title “Global Environmental Change” was
deemed most appropriate
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Bizarro
By Don Piraro
04-05-07
O8-08-03
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