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Climate change

Fisika lingkungan

2007

Pfis-fkip untanls


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1. Has the climate changed during the

20th century?

Yes, many observations indicate that the world's climate haschanged during the 20th century:

1.1. The average surface temperature has increased by about0.6C (1F).

Snow cover and ice extent have decreased.The sea level has risen by 10 to 20 cm (4 to 8").

1.2. Some other important changes include precipitation, cloudcover and extreme temperatures.

1.3. Some important aspects appear NOT to have changed, like

Antarctic sea-ice extent or extreme events such as storms,tornadoes, thunder days, or hail events.


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2. What causes this climate change?

2.1. Climate has and will always vary for natural reasons.However, human activities are increasing significantlythe concentrations of some gases in the atmosphere,

such as greenhouse gases (mainly CO2), which tend towarm the earth surface, and anthropogenic aerosol,which mostly tend to cool it.

2.2. Although more research is needed, understanding ofclimate processes and computer models have improvedleading the IPCC to draw the following conclusion: Mostof the warming over the last 50 years is likely to havebeen due to man-made activities.


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3. What climate changes are expected for

the future?

3.1. To predict the future climate, several greenhouse gas emissionscenarios were developed and fed into computer models

3.2. They project for the next century that, without specific policychanges : global mean temperature should increase by between 1.4 and 5.8C (2.5 to

10F). the Northern Hemisphere cover should decrease further, but the Antarcticice sheet should increase.

the sea level should rise by between 9 and 88 cm (3.5" to 35"). other changes should occur, including an increase in some extreme

weather events.

3.3. After 2100, human induced climate change is projected to persist for

many centuries.The sea level should continue rising for thousands of years after theclimate has been stabilized.


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4. What are the likely consequences of

climate change?

4.1. Regional changes in climate, particularly increases in temperature,have already affected some physical and biological systems.

4.2. Both natural and human systems are vulnerable to climate changebecause of their limited adaptive capacity. This vulnerability varieswith geographic location, time, and social, economic andenvironmental conditions.

4.3. Some extreme weather events and the damage, hardship, and deaththey cause are projected to increase with global warming. There isalso a potential for large-scale and possibly irreversible impacts whichpose risks that have yet to be reliably quantified; their likelihood isprobably very low but is expected to increase with the rate, magnitude,and duration of climate change

4.4. Man will have to adapt to and cope with the climate change

consequences that are not prevented by mitigation. Economic lossescan be expected, especially in poorest regions; the higher thewarming, the greater the losses. Promoting adaptation, sustainabledevelopment and equity can be mutually reinforcing.


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5. How could Climate Change affect us in

the future?

5.1. Projected changes in climate are expected to have bothbeneficial and adverse effects on water resources, agriculture,natural ecosystems and human health. But the larger thechanges in climate the more the adverse effects shoulddominate. For instance, some crop and forest productivitiescould benefit from a small climate change. But for many other

natural systems, the adverse effects should be dominant,especially if warming exceeds a few degrees.

5.2. Human populations are expected to face increasing floodingand heat waves but reduced cold spells. The geographic rangefor infectious diseases should increase.

5.3. The vulnerability of human populations and natural systems

to climate change differs substantially across regions andacross populations within regions.


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6. How could greenhouse gas emissions

be reduced?

6.1.climate change is a unique, global, long-term problem, involvingcomplex interactions.

6.2. There are many technological options for reducing greenhouseemissions, some at low or negative cost. Forests and agriculturallands provide significant but not necessarily permanent carbon sinks,which may allow time for other options.

6.3. There will be both costs and benefits to reducing greenhouse gases.Most studies project that in 2010, the Kyoto Protocol should costdeveloped countries a reduction in projected GDP of about 0.2% to 2%without emission trading and about half of that with emission trading.

6.4. Greenhouse gas reduction programs need to overcome manybarriers. Governments have a wide array of instruments at theirdisposal. With coordinated actions and international regimes,

efficiency and equity should improve.6.5. Further research is required to strengthen future assessments and to

reduce uncertainties.


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8. Do man-made greenhouse gases

matter compared to water vapor?

Water vapor is by far the most importantgreenhouse gas Nevertheless, the man-made increase in other greenhouse gases

such as CO2 is expected to induce someadditional warming in the coming decades.Warmer air contains more water vapor;this in turn amplifies the man-made

warming. Other reactive mechanisms(feedback) could both amplify or reducethis warming.


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9. Can ecosystems adapt to Climate

Change?

Ecosystems have a limited capacity to adapt toclimate change; some might not be able to copeas they had done in earlier periods and areexpected to suffer damages because:

The rate and extent of climate change isexpected to be faster and greater than in the pastand could exceed nature's maximum adaptationspeed;

Human activities and pollution have increased thevulnerability of ecosystems


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10. What is and is not known with

certainty about climate change?

10.1. The earth's average surface temperature hasincreased by about 0.6 C (1F) during last century, andhuman activities are increasing the levels of greenhousegases which tends to warm the planet.

10.2. How much and how fast temperatures will continue torise remains uncertain, and the exact impacts of climatechange over the 21st century, especially for localregions, remain largely unknown.

10.4. However, global warming poses real risks. Becausethe exact nature and amplitude of these risks remainsuncertain, we have to use our best judgment guided bythe current state of science to determine what the mostappropriate response should be.


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11. Conclusion

The earth's climate has changed over the last century (see 1). There isnew and stronger evidence that most of the warming observed the last

50 years is attributable to human activities (see 2.3). Evolvingcomputer models (see 2.2) are predicting that, because of greenhouseemissions, temperatures should continue to rise over the 21st century(see 3), impacting nature and mankind both positively and negatively(see 4 dan 5).

The impacts should vary among regions (see 5.3), but they can not yet bepredicted accurately, especially for small-scale areas (see 10.3).

However, it is expected that:the more the greenhouse gases are emitted, the higher the tendency

for the earth to warm (see 3.2),

the greater and faster the warming, the more the adverse effects willdominate (see 5),

and the higher the possibility, although probably remote, of large-scale and possibly irreversible impacts (see 4.3).

Therefore, although an acceptable level for greenhouse gases has not yetbeen determined, reducing emissions should reduce the risk ofadverse effects. Many options for emission reductions are available(see 6.2); their costs need to be balanced with the risks left for futuregenerations.


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Climate change

2007Fisika lingkungan

2007

Pfis-fkip untanls


14/24


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2. How is climate changing and how has it

changed in the past?

changes in temperature, sea level and snow cover since 1850

2.1 The warming of global climate is now unequivocal. There are manyobservations of increasing air and ocean temperatures, widespread meltingof snow and ice, and rising sea levels. More specifically, eleven of the lasttwelve years (1995-2006) rank among the 12 warmest years ever recordedsince global surface temperatures are measured (1850). Over the last 100

years (19062005), global temperature has increased by 0.74C. Globalsea level has risen by 17 cm during the 20th century, in part because of themelting of snow and ice from many mountains and in the polar regions.More regional changes have also been observed, including changes inArctic temperatures and ice, ocean salinity, wind patterns, droughts,precipitations, frequency of heat waves and intensity of tropical cyclones.

2.2 The temperatures of the last half century are unusual in comparison withthose of at least the previous 1300 years. The last time that the polarregions remained significantly warmer than now for a very extended period(125 000 years ago), the sea level rose by 4 to 6 meters.

2.3 Most of the increase in global temperature observed over the past fiftyyears is very likelydue to human emissions ofgreenhouse gases.
http://www.greenfacts.org/en/climate-change-ar4/figtableboxes/figure-3.htmhttp://www.greenfacts.org/glossary/pqrs/salinity.htmhttp://www.greenfacts.org/en/climate-change-ar4/toolboxes/likelihood.htmhttp://www.greenfacts.org/glossary/ghi/greenhouse-gas.htmhttp://www.greenfacts.org/glossary/ghi/greenhouse-gas.htmhttp://www.greenfacts.org/en/climate-change-ar4/toolboxes/likelihood.htmhttp://www.greenfacts.org/glossary/pqrs/salinity.htmhttp://www.greenfacts.org/en/climate-change-ar4/figtableboxes/figure-3.htmhttp://www.greenfacts.org/en/climate-change-ar4/figtableboxes/figure-3.htm


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3. How is the climate going to change in

the future?

From 1980 to the end of the 21st century, temperatures are projected to increase by1.8C to 4.0C.

3.1 The global average temperature is expected to increase by about 0.2C per decadeover the next two decades. Continuing greenhouse gas emissions at or above currentrates would cause a further increase in global temperatures and many other climaticchanges during the 21st century.The best estimates for projected global temperature

increases from the 1980s to the end of the 21st century range from 1.8C (1.1 -2.9C) to 4C (2.4 - 6.4C) for the IPCC scenarios that do not consider additionalmitigation measures apart from those already in place in 2000.

3.2 Global average sea level is expected to rise by 18 to 59 cm by the end of the 21stcentury. Warming is expected to be greatest over land and at high northern latitudesand smallest over the Southern Ocean and parts of the North Atlantic Ocean. Otherprojected changes include acidification of the oceans, reduced snow cover andsea ice, more frequent heat waves and heavy precipitation, more intense tropical

cyclones, and slower oceanic currents.

3.3 Warming and sea level rise caused by human activities will continue for centuries,even ifgreenhouse gas concentrations were to be stabilized. If warming persists overmany centuries, it could lead to a complete melting of the Greenland Ice sheet,increasing global sea levels by about 7m
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What impacts of climate change have

already been observed?

Glaciers are melting in many places across the world. Regional climate change is already affecting many natural systems.

For instance, it is increasingly being observed that snow and ice aremelting and frozen ground is thawing, hydrological and biologicalsystems are changing and in some cases being disrupted,migrations are starting earlier, and species' geographic ranges are

shifting towards the poles. Despite remaining gaps in knowledge, it is likely that these effects

are linked to human influence on climate. At the regional level,however, responses to natural variability are difficult to separatefrom the effects ofclimate change.

Some previously unanticipated impacts of regional climate change

are just starting to become apparent. For instance, melting glacierscan threaten mountain settlements and water resources, anddamage associated with coastal flooding are increasing.
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5. What impacts are expected in the future?

5.1 Over the course of the 21st century, many impacts are expected to occur in naturalsystems. For instance, changes in precipitation and the melting of ice and snow areexpected to increase flood risks in some areas while causing droughts in others. If

there is significant warming the capacity ofecosystems to adapt will be exceeded,with negative consequences such as an increased risk of extinction ofspecies.

5.2 The most vulnerable people are in general the poor, since they have less capacity toadapt, and their livelihoods are often dependent on resources that are linked toclimate.

5.3 Africa is found to be particularly vulnerable to climate change, because of existingpressures on its ecosystems and its low capacity to adapt. On all continents, watersupply and the threat to coastal areas will be an issue. Overall future impacts areexpected to be negative, although some positive effects are also expected initially,such as an increase in agricultural productivity at high latitudes accompanying amoderate warming, or decreased heating needs in cold regions.

5.4 Impacts will depend on the magnitude of the temperature increase. For instance,some crops at mid- to high latitudes will have higherproductivity if local temperatureincreases by 1-3 C, but will be negatively affected beyond that (see Table ). If highertemperatures persist after the 21st century it could result in very large impacts. Forinstance, the large sea-level rise that would result from the melting of the Greenlandand Antarctic ice sheets would have major repercussions on coastal areas. The costassociated with the effects ofclimate change is projected to increase over time withrising temperatures.

5.5 A projected increase in the severity and frequency of droughts, heat waves, and otherextreme weather events is expected to cause major impacts over the course of thiscentury
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7. What are the current trends in

greenhouse gas emissions?

Global greenhouse gas emissions have grown markedlysince pre-industrial times, with a 70% increase from1970 to 2004 alone . Over this period, emissions fromthe transport and energy sectors have more thandoubled. Policies put in place in some countries have

been effective in reducing emissions in those countriesto a certain degree, but not sufficiently to counteract theglobal growth in emissions.

Without additional measures to mitigate climate change,global green house gas emissions will continue to grow

over the coming decades and beyond. Most of thisincrease would come from developing countries, whereper capita emissions are still considerably lower thanthose in developed countries.
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8. What actions can be taken to reduce

greenhouse gas emissions?8.1 Mitigation measures to reduce greenhouse gas emissions have a certain cost. However,

they also constitute an economic benefit by reducing the impacts ofclimate change, and

the costs associated with them. In addition, they can bring economic benefits by reducinglocal air pollution and energy resource depletion. If the benefits of avoided climate changeare taken into account and a carbon price is established for each unit ofgreenhouse gasemissions, this could create incentives for producers and consumers to significantly investin products, technologies and processes which emit less greenhouse gases. 8.2 Changesin lifestyle and behaviours that favor resource conservation can contribute toclimate change mitigation.

8.3 Mitigation measures can also have other benefits for society, such as health cost savings

resulting from reduced air pollution. However, mitigation in one country or group ofcountries could lead to higher emissions elsewhere or effects on the global economy.

8.4 No one sector or technology can address the entire mitigation challenge. All sectorsincluding buildings, industry, energy production, agriculture, transport, forestry, and wastemanagement could contribute to the overall mitigation efforts, for instance through greaterenergy efficiency. Many technologies and processes which emit less greenhouse gasesare already commercially available or will be in the coming decades

8.5 In order to stabilize the concentration ofgreenhouse gases in the atmosphere, emissionswould have to stop increasing and then decline. The lower the stabilization level aimed for,the more quickly this decline would need to occur. World-wide investments in mitigationtechnologies, as well as research into new energy sources, will be necessary to achievestabilization. Delaying emission reduction measures limits the opportunities to achieve lowstabilization levels and increases the risk of severe climate change impacts
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9. How can governments create incentives for

mitigation?

9.1 A wide variety of policy tools can be applied by governments to createincentives for mitigation action, such as regulation, taxation, tradablepermit schemes, subsidies, and voluntary agreements. Past experienceshows that there are advantages and drawbacks for any given policyinstrument. For instance, while regulations and standards can providesome certainty about emission levels, they may not encourageinnovations and more advanced technologies.

Although the impact of the Kyoto protocols first commitment period 2008-

2012 on global carbon emissions is expected to be limited, it has allowedthe establishment of a global response to the climate problem as well asthe creation of an international carbon market and other mechanisms thatmay provide the foundation for future mitigation efforts.

9.2 Switching to more sustainable development paths can make a majorcontribution to climate change mitigation. Policies that contribute to bothclimate change mitigation and sustainable development include those

related to energy efficiency, renewable energies, and conservation ofnatural habitats. In general, sustainable development can increase thecapacity foradaptation and mitigation, and reduce vulnerability to theimpacts of climate change.
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10. Conclusion Current warming trends are unequivocal. It is very likely that

greenhouse gases released by human activities are responsible for most ofthe warming observed in the past fifty years. The warming is projected to

continue and to increase over the course of the 21st century and beyond. Climate change already has a measurable impact on many natural and

human systems. Effects are projected to increase in the future and to bemore severe with greater increases in temperature. Adaptation measuresare already being implemented, and will be essential in order to address theprojected consequences. There is, however, a limit to adaptation; mitigationmeasures will also be needed in order to reduce the severity of impacts.

Mitigation measures that aim to reduce greenhouse gas emissions can helpavoid, reduce or delay many impacts ofclimate change. Policy instrumentscould create incentives for producers and consumers to significantly investin products, technologies and processes which emit less greenhouse gases.Without new mitigation policies, global greenhouse gas emissions willcontinue to grow over the coming decades and beyond. Rapid world-wideinvestments and deployment of mitigation technologies, as well as research

into new energy sources will be necessary to achieve a stabilization of theconcentration of greenhouse gases in the atmosphere. Additional research addressing gaps in knowledge would further reduce

uncertainties and thus facilitate decision-making related to climate change.
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12. Other views

This summary is based on the latestIntergovernmental Panel on Climate Change

(IPPC) review, the Third Assessment Report(TAR)

It is considered by most scientists as a consensusdocument and other recent scientific

assessments reach similar conclusions.However, some people and organizationsdisagree with certain IPCC conclusions

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