The economic analysis of climate change explains how economic thinking, tools and techniques are applied to calculate the magnitude and distribution of damage caused by climate change. It also informs the policies and approaches for mitigation and adaptation to climate change from global to household scales. This topic is also inclusive of alternative economic approaches, including ecological economics and degrowth.
Economic analysis of climate change is considered challenging as it is a long-term problem and has substantial distributional issues within and across countries. Furthermore, it engages with uncertainty about the physical damages of climate changes, human responses, and future socioeconomic development.
Sub-topics within the economic analysis concept are the economic impacts of climate change, as well as the economics of climate change mitigation.
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Effects of climate change may last a long time, such as sea level rise which will not be reversed for thousands of years. [1] : SPM-21 The long time scales and uncertainty associated with global warming have led analysts to develop "scenarios" of future environmental, social and economic changes. [2] These scenarios can help governments understand the potential consequences of their decisions.
One of the economic aspects of climate change is producing scenarios of future economic development. Future economic developments can, for example, affect how vulnerable society is to future climate change, [3] what the future impacts of climate change might be, as well as the level of future GHG emissions. [4]
In scenario analysis, scenarios are developed that are based on differing assumptions of future development patterns. [2] An example of this are the shared socioeconomic pathways produced by the Intergovernmental Panel on Climate Change (IPCC). These project a wide range of possible future emissions levels.
Some analysts have developed scenarios that project a continuation of current policies into the future. These scenarios are sometimes called "business-as-usual" scenarios. [5] : 176
Experts who work on scenarios tend to prefer the term "projections" to "forecasts" or "predictions". [6] This distinction is made to emphasize the point that probabilities are not assigned to the scenarios, [6] and that future emissions depend on decisions made both now and into the future. [7] : 75
Another approach is that of uncertainty analysis, [2] where analysts attempt to estimate the probability of future changes in emission levels.
Standard cost–benefit analysis (CBA) [12] (also referred to as a monetized cost–benefit framework) [13] has been applied to the problem of climate change. [14] This requires (1) the valuation of costs and benefits using willingness to pay (WTP) or willingness to accept (WTA) compensation [13] [15] [16] [17] as a measure of value, [12] and (2) a criterion for accepting or rejecting proposals: [12]
For (1), in CBA where WTP/WTA is used, climate change impacts are aggregated into a monetary value, [13] with environmental impacts converted into consumption equivalents, [18] and risk accounted for using certainty equivalents. [18] [19] Values over time are then discounted to produce their equivalent present values. [20]
The valuation of costs and benefits of climate change can be controversial [21] : 936–938 because some climate change impacts are difficult to assign a value to, e.g., ecosystems and human health. [22] [23] It is also impossible to know the preferences of future generations, which affects the valuation of costs and benefits. [24] : 4 Another difficulty is quantifying the risks of future climate change. [25]
For (2), the standard criterion is the Kaldor-Hicks [24] : 3 compensation principle. [12] According to the compensation principle, so long as those benefiting from a particular project compensate the losers, and there is still something left over, then the result is an unambiguous gain in welfare. [12] If there are no mechanisms allowing compensation to be paid, then it is necessary to assign weights to particular individuals. [12]
One of the mechanisms for compensation is impossible for this problem: mitigation might benefit future generations at the expense of current generations, but there is no way that future generations can compensate current generations for the costs of mitigation. [24] : 4 On the other hand, should future generations bear most of the costs of climate change, compensation to them would not be possible. [14] Another transfer for compensation exists between regions and populations. If, for example, some countries were to benefit from reducing climate change but others lose out, there would be no guarantee that the winners would compensate the losers. [14]
In a cost–benefit analysis, an acceptable risk means that the benefits of a climate policy outweigh the costs of the policy. [25] The standard rule used by public and private decision makers is that a risk will be acceptable if the expected net present value is positive. [25] The expected value is the mean of the distribution of expected outcomes. [26] : 25 In other words, it is the average expected outcome for a particular decision. This criterion has been justified on the basis that:
On the first point, probabilities for climate change are difficult to calculate. [25] Although some impacts, such as those on human health and biodiversity, are difficult to value [25] it has been estimated that 3.5 million people die prematurely each year from air pollution from fossil fuels. [27] The health benefits of meeting climate goals substantially outweigh the costs of action. [28] According to Andrew Haines at the London School of Hygiene & Tropical Medicine the health benefits of phasing out fossil fuels measured in money (estimated by economists using the value of life for each country) are substantially more than the cost of achieving the 2 degree C goal of the Paris Agreement. [29]
On the second point, it has been suggested that insurance could be bought against climate change risks. [25] Policymakers and investors are beginning to recognize the implications of climate change for the financial sector, from both physical risks (damage to property, infrastructure, and land) and transition risk due to changes in policy, technology, and consumer and market behavior. Financial institutions are becoming increasingly aware of the need to incorporate the economics of low carbon emissions into business models. [30]
The economic impacts of climate change vary geographically and are difficult to forecast exactly. Researchers have warned that current economic forecasts may seriously underestimate the effects of climate change, and point to the need for new models that give a more accurate picture of potential damages. Nevertheless, one 2018 study found that potential global economic gains if countries implement mitigation strategies to comply with the 2 °C target set at the Paris Agreement are in the vicinity of US$17 trillion per year up to 2100 compared to a very high emission scenario. [32] A study by the reinsurance company Swiss Reinsurance Company Ltd (Swiss Re) in 2021 estimated that global climate change is likely to reduce global economic output by 11-14%, or as much as $23 trillion annually by 2050, compared with global economic output without climate change. According to this study, the economies of wealthy countries like the United States would likely shrink by approximately 7% while some developing nations would be devastated, losing around 20% or in some cases 40% of the their economic output. [33]
Global losses reveal rapidly rising costs due to extreme weather events since the 1970s. [34] Socio-economic factors have contributed to the observed trend of global losses, such as population growth and increased wealth. [35] Part of the growth is also related to regional climatic factors, e.g., changes in precipitation and flooding events. It is difficult to quantify the relative impact of socio-economic factors and climate change on the observed trend. [36] The trend does, however, suggest increasing vulnerability of social systems to climate change. [36]In the scientific literature, there is sometimes a focus on "best estimate" or "likely" values of climate sensitivity. [39] However, from a risk management perspective, values outside of "likely" ranges are relevant, because, though these values are less probable, they could be associated with more severe climate impacts [40] (the statistical definition of risk = probability of an impact × magnitude of the impact). [41] : 208
Analysts have also looked at how uncertainty over climate sensitivity affects economic estimates of climate change impacts. [42] Policy guidance from cost-benefit analysis (CBA) can be extremely divergent depending on the assumptions employed. [43] Hassler et al use integrated assessment modeling to examine a range of estimates and what happens at extremes. [44]
One of the problems of climate change are the large uncertainties over the potential impacts of climate change, and the costs and benefits of actions taken in response to climate change, e.g., in reducing GHG emissions. [45] : 608 Two related ways of thinking about the problem of climate change decision-making in the presence of uncertainty are iterative risk management [46] [41] and sequential decision making [47] : 612–614 Considerations in a risk-based approach might include, for example, the potential for low-probability, worst-case climate change impacts. [48]
One of the responses to the uncertainties of global warming is to adopt a strategy of sequential decision making. [49] Sequential decision making refers to the process in which the decision maker makes consecutive observations of the process before making a final decision. [50] This strategy recognizes that decisions on global warming need to be made with incomplete information, and that decisions in the near term will have potentially long-term impacts. Governments may use risk management as part of their policy response to global warming. [51] [41] : 203
An approach based on sequential decision making recognises that, over time, decisions related to climate change can be revised in the light of improved information. [49] This is particularly important with respect to climate change, due to the long-term nature of the problem. A near-term hedging strategy concerned with reducing future climate impacts might favour stringent, near-term emissions reductions. [47] As stated earlier, carbon dioxide accumulates in the atmosphere, and to stabilize the atmospheric concentration of CO2, emissions would need to be drastically reduced from their present level (refer to diagram opposite). [37] Stringent near-term emissions reductions allow for greater future flexibility with regard to a low stabilization target, e.g., 450 parts-per-million (ppm) CO2. To put it differently, stringent near-term emissions abatement can be seen as having an option value in allowing for lower, long-term stabilization targets. This option may be lost if near-term emissions abatement is less stringent. [52]
On the other hand, a view may be taken that points to the benefits of improved information over time. This may suggest an approach where near-term emissions abatement is more modest. [53] Another way of viewing the problem is to look at the potential irreversibility of future climate change impacts (e.g., damages to ecosystems) against the irreversibility of making investments in efforts to reduce emissions. [49]
Granger Morgan et al. (2009) [38] suggested two related decision-making management strategies that might be particularly appealing when faced with high uncertainty. The first were resilient strategies. This seeks to identify a range of possible future circumstances, and then choose approaches that work reasonably well across all the range. The second were adaptive strategies. The idea here is to choose strategies that can be improved as more is learned as the future progresses. Granger Morgan contrasted these two approaches with the cost–benefit approach, which seeks to find an optimal strategy. [38]
An example of a strategy that is based on risk is portfolio theory. This suggests that a reasonable response to uncertainty is to have a wide portfolio of possible responses. In the case of climate change, mitigation can be viewed as an effort to reduce the chance of climate change impacts. [26] : 24 Adaptation acts as insurance against the chance that unfavourable impacts occur. [54] The risk associated with these impacts can also be spread.[ clarification needed ] As part of a policy portfolio, climate research can help when making future decisions. Technology research can help to lower future costs.
The optimal result of decision analysis depends on how "optimal" is defined. [55] Decision analysis requires a selection criterion to be specified. In a decision analysis based on monetized cost–benefit analysis (CBA), the optimal policy is evaluated in economic terms. The optimal result of monetized CBA maximizes net benefits. Another type of decision analysis is cost-effectiveness analysis. Cost-effectiveness analysis aims to minimize net costs.
Monetized CBA may be used to decide on the policy objective, e.g., how much emissions should be allowed to grow over time. The benefits of emissions reductions are included as part of the assessment.
Unlike monetized CBA, cost-effectiveness analysis does not suggest an optimal climate policy. For example, cost-effectiveness analysis may be used to determine how to stabilize atmospheric greenhouse gas concentrations at lowest cost. However, the actual choice of stabilization target (e.g., 450 or 550 ppm carbon dioxide equivalent), is not "decided" in the analysis.
The choice of selection criterion for decision analysis is subjective. [55] The choice of criterion is made outside of the analysis (it is exogenous). One of the influences on this choice on this is attitude to risk. Risk aversion describes how willing or unwilling someone is to take risks. Evidence indicates that most, but not all, individuals[ clarification needed ] prefer certain outcomes to uncertain ones. Risk-averse individuals prefer decision criteria that reduce the chance of the worst possible outcome, while risk-seeking individuals prefer decision criteria that maximize the chance of the best possible outcome. In terms of returns on investment, if society as a whole is risk-averse, we might be willing to accept some investments with negative expected returns, e.g., in mitigation. [56] Such investments may help to reduce the possibility of future climate damages or the costs of adaptation.
Since 2021 the cost of new wind and solar power has generally been less than existing gas and coal-fired power: [57] both because of the rise in price of natural gas that year and the long-term trend of falling renewables prices. [58] However it is estimated that the steady growth part of the S-shaped growth curve of renewable power will not be enough on its own to meet the goal of the Paris Agreement to limit global warming to 1.5 degrees. [58] According to the World Resources İnstitute both non-economic and economic policies are needed to increase the rate of growth of renewables: for example they say some countries should invest more in upgrading power grids. [58]
The distribution of benefits from adaptation and mitigation policies are different in terms of damages avoided. [59] : 653 Adaptation activities mainly benefit those who implement them, while mitigation benefits others who may not have made mitigation investments. Mitigation can therefore be viewed as a global public good, while adaptation is either a private good in the case of autonomous adaptation, or a national or regional public good in the case of public sector policies. Climate change mitigation consist of human actions to reduce greenhouse gas emissions or to enhance carbon sinks that absorb greenhouse gases from the atmosphere. [60] : 2239
In a cost–benefit analysis, the trade offs between climate change impacts, adaptation, and mitigation are made explicit. Cost–benefit analyses of climate change are produced using integrated assessment models (IAMs), which incorporate aspects of the natural, social, and economic sciences.
In an IAM designed for cost–benefit analysis, the costs and benefits of impacts, adaptation and mitigation are converted into monetary estimates. Some view the monetization of costs and benefits as controversial (see Economic impacts of climate change#Aggregate impacts). The "optimal" levels of mitigation and adaptation are then resolved by comparing the marginal costs of action with the marginal benefits of avoided climate change damages. [59] : 654 The decision over what "optimal" is depends on subjective value judgements made by the author of the study. [61]
There are many uncertainties that affect cost–benefit analysis, for example, sector- and country-specific damage functions. [59] : 654 Another example is with adaptation. The options and costs for adaptation are largely unknown,[ citation needed ] especially in developing countries.
A common finding of cost–benefit analysis is that the optimum level of emissions reduction is modest in the near-term, with more stringent abatement in the longer-term. [62] : 298 [63] : 20 [64] [ better source needed ] This approach might lead to a warming of more than 3 °C above the pre-industrial level. [65] : 8 [ better source needed ] In most models, benefits exceed costs for stabilization of GHGs leading to warming of 2.5 °C. No models suggest that the optimal policy is to do nothing, i.e., allow "business-as-usual" emissions.
Along the efficient emission path calculated by Nordhaus and Boyer in 2000, the long-run global average temperature after 500 years increases by 6.2 °C above the 1900 level. [66] Nordhaus and Boyer stated their concern over the potentially large and uncertain impacts of such a large environmental change. The projected temperature in this IAM, like any other, is subject to scientific uncertainty (e.g., the relationship between concentrations of GHGs and global mean temperature, which is called the climate sensitivity). Projections of future atmospheric concentrations based on emission pathways are also affected by scientific uncertainties, e.g., over how carbon sinks, such as forests, will be affected by future climate change. Klein et al. (2007) concluded that there were few high quality studies in this area, and placed low confidence in the results of cost–benefit analysis. [67]
In spite of various uncertainties or possible criticisms of cost–benefit analysis, it does have several strengths:
Some have said that economic growth is a key driver of CO2 emissions. [70] : 707 [ better source needed ] [71] [ contradictory ] [72] [73] However later (in late 2022) others have said that economic growth no longer means higher emissions. [74] As the economy expands, demand for energy and energy-intensive goods increases, pushing up CO2 emissions. On the other hand, economic growth may drive technological change and increase energy efficiency. Economic growth may be associated with specialization in certain economic sectors. If specialization is in energy-intensive sectors, specifically carbon energy sources, then there will be a strong link between economic growth and emissions growth. If specialization is in less energy-intensive sectors, e.g. the services sector, then there might be a weak link between economic growth and emissions growth.
Much of the literature focuses on the "environmental Kuznets curve" (EKC) hypothesis, which posits that at early stages of development, pollution per capita and GDP per capita move in the same direction. Beyond a certain income level, emissions per capita will decrease as GDP per capita increase, thus generating an inverted-U shaped relationship between GDP per capita and pollution. However, the econometrics literature did not support either an optimistic interpretation of the EKC hypothesis – i.e., that the problem of emissions growth will solve itself – or a pessimistic interpretation – i.e., that economic growth is irrevocably linked to emissions growth. [70] Instead, it was suggested that there was some degree of flexibility between economic growth and emissions growth. [75]
Mitigation cost estimates depend on the baseline (in this case, a reference scenario that the alternative scenario is compared with), the way costs are modelled, and assumptions about future government policy. [76] : 622 Cost estimates for mitigation for specific regions are dependent on the quantity of emissions "allowed" for that region in future, as well as the timing of interventions. [77] : 90
Mitigation costs will vary according to how and when emissions are cut: early, well-planned action will minimise the costs. [78] Globally, the benefits of keeping warming under 2 °C exceed the costs. [79]
Many economists estimate the cost of climate change mitigation at between 1% and 2% of GDP. [80] One 2018 estimate stated that temperature increase can be limited to 1.5 °C for 1.7 trillion dollars a year. [81] [82] According to this study, a global investment of approximately $1.7 trillion per year would have been needed to keep global warming below 1.5°C. Whereas this is a large sum, it is still far less than the subsidies governments provided to the ailing fossil fuel industry, estimated at more than $5 trillion per year by the International Monetary Fund. [83] [84] However by the end of 2022 many thought limiting to 1.5 °C politically impossible. [85]
The economic repercussions of mitigation vary widely across regions and households, depending on policy design and level of international cooperation. Delayed global cooperation increases policy costs across regions, especially in those that are relatively carbon intensive at present. Pathways with uniform carbon values show higher mitigation costs in more carbon-intensive regions, in fossil-fuels exporting regions and in poorer regions. Aggregate quantifications expressed in GDP or monetary terms undervalue the economic effects on households in poorer countries; the actual effects on welfare and well-being are comparatively larger. [86]
Cost–benefit analysis may be unsuitable for analysing climate change mitigation as a whole but still useful for analysing the difference between a 1.5 °C target and 2 °C. [80] One way of estimating the cost of reducing emissions is by considering the likely costs of potential technological and output changes. Policy makers can compare the marginal abatement costs of different methods to assess the cost and amount of possible abatement over time. The marginal abatement costs of the various measures will differ by country, by sector, and over time. [78]Economists generally agree on the following two principles: [26] : 29
Some early studies suggested that a uniform carbon tax would be a fair and efficient way of reducing emissions. [88] : 103–104 A carbon tax is a Pigouvian tax, and taxes fuels based on their carbon content. [89] : 92 A literature assessment by Banuri et al. [88] : 103–104 summarized criticisms of such a system:
An alternative approach to having a Pigouvian tax is one based on property rights. A practical example of this would be a system of emissions trading, which is essentially a privatization[ clarification needed ] of the atmosphere. [93] The idea of using property rights in response to an externality was put forward by Ronald Coase in The Problem of Social Cost (1960). Coase's model of social cost assumes a situation of equal bargaining power among participants and equal costs of making the bargain. [59] : 668 Assigning property rights can be an efficient solution.[ clarification needed ] This is based on the assumption that there are no bargaining/transaction costs involved in buying or selling these property rights, and that buyers and sellers have perfect information available when making their decisions.
If these assumptions are correct, efficiency is achieved regardless of how property rights are allocated. In the case of emissions trading, this suggests that equity and efficiency can be addressed separately: equity is taken care of in the allocation of emission permits, and efficiency is promoted by the market system. In reality, however, markets do not live up to the ideal conditions that are assumed in Coase's model, with the result that there may be trade-offs between efficiency and equity. [94]
No consensus exists on who should bear the burden of adaptation and mitigation costs. [26] : 29 Several different arguments have been made over how to spread the costs and benefits of taxes or systems based on emissions trading.
One approach considers the problem from the perspective of who benefits most from the public good. This approach is sensitive to the fact that different preferences exist between different income classes. The public good is viewed in a similar way as a private good, where those who use the public good must pay for it. Some people will benefit more from the public good than others, thus creating inequalities in the absence of benefit taxes. A difficulty with public goods is determining who exactly benefits from the public good, although some estimates of the distribution of the costs and benefits of global warming have been made – see above. Additionally, this approach does not provide guidance as to how the surplus of benefits from climate policy should be shared.
A second approach has been suggested based on economics and the social welfare function. To calculate the social welfare function requires an aggregation of the impacts of climate change policies and climate change itself across all affected individuals. This calculation involves a number of complexities and controversial equity issues. [15] : 460 For example, the monetization of certain impacts on human health. There is also controversy over the issue of benefits affecting one individual offsetting negative impacts on another. [21] : 958 These issues to do with equity and aggregation cannot be fully resolved by economics. [88] : 87
On a utilitarian basis, which has traditionally been used in welfare economics, an argument can be made for richer countries taking on most of the burdens of mitigation. [95] However, another result is possible with a different modeling of impacts. If an approach is taken where the interests of poorer people have lower weighting, the result is that there is a much weaker argument in favour of mitigation action in rich countries. Valuing climate change impacts in poorer countries less than domestic climate change impacts (both in terms of policy and the impacts of climate change) would be consistent with observed spending in rich countries on foreign aid [96] [97] : 229
In terms of the social welfare function, the different results depend on the elasticity of marginal utility. A declining marginal utility of consumption means that a poor person is judged to benefit more from increases in consumption relative to a richer person. A constant marginal utility of consumption does not make this distinction, and leads to the result that richer countries should mitigate less.[ clarification needed ]
A third approach looks at the problem from the perspective of who has contributed most to the problem. Because the industrialized countries have contributed more than two-thirds of the stock of human-induced GHGs in the atmosphere, this approach suggests that they should bear the largest share of the costs. This stock of emissions has been described as an "environmental debt". [98] : 167 In terms of efficiency, this view is not supported. This is because efficiency requires incentives to be forward-looking, and not retrospective. [26] : 29 The question of historical responsibility is a matter of ethics. Munasinghe et al. suggested that developed countries could address the issue by making side-payments to developing countries. [98] : 167
It is often argued in the literature that there is a trade-off between adaptation and mitigation, in that the resources committed to one are not available for the other. [99] : 94 [ better source needed ] This is debatable in practice because the people who bear emission reduction costs or benefits are often different from those who pay or benefit from adaptation measures.
There is also a trade off in how much damage from climate change should be avoided. The assumption that it is always possible to trade off different outcomes is viewed as problematic by many people. [100]
Some of the literature has pointed to difficulties in these kinds of assumptions. For instance, there may be aversion at any price towards losing particular species. [101] This is related to climate change, since the possibility of future abrupt changes in the climate or the Earth system cannot be ruled out. For example, if the West Antarctic ice sheet was to disintegrate, it could result in a sea level rise of 4–6 meters over several centuries.
Traditional insurance works by transferring risk to those better able or more willing to bear risk, and also by the pooling of risk. [26] : 25 Since the risks of climate change are, to some extent, correlated, this reduces the effectiveness of pooling. However, there is reason to believe that different regions will be affected differently by climate change. This suggests that pooling might be effective. Since developing countries appear to be potentially most at risk from the effects of climate change, developed countries could provide insurance against these risks. [102]
Disease, rising seas, reduced crop yields, and other harms driven by climate change will likely have a major deleterious impact on the economy by 2050 unless the world sharply reduces greenhouse gas emissions in the near term, according to a number of studies, including a study by the Carbon Disclosure Project and a study by insurance giant Swiss Re. The Swiss Re assessment found that annual output by the world economy will be reduced by $23 trillion annually, unless greenhouse gas emissions are adequately mitigated. As a consequence, according to the Swiss Re study, climate change will impact how the insurance industry prices a variety of risks. [103] [104] [105]
Authors have pointed to several reasons why commercial insurance markets cannot adequately cover risks associated with climate change. [106] : 72 For example, there is no international market where individuals or countries can insure themselves against losses from climate change or related climate change policies.[ clarification needed ]
Financial markets for risk
There are several options for how insurance could be used in responding to climate change. [106] : 72 One response could be to have binding agreements between countries. Countries suffering greater-than-average climate-related losses would be assisted by those suffering less-than-average losses. This would be a type of mutual insurance contract.
These two approaches would allow for a more efficient distribution of climate change risks. They would also allow for different beliefs over future climate outcomes. For example, it has been suggested that these markets might provide an objective test of the honesty of a particular country's beliefs over climate change. Countries[ which? ] that honestly believe that climate change presents little risk[ clarification needed ] would be more prone to hold securities against these risks.
As stated, there is considerable uncertainty over decisions regarding climate change, as well as different attitudes over how to proceed, e.g., attitudes to risk and valuation of climate change impacts. Risk management can be used to evaluate policy decisions based a range of criteria or viewpoints, and is not restricted to the results of particular type of analysis, e.g., monetized CBA. [107] : 42 Some authors have focused on a disaggregated analysis of climate change impacts. [108] : 23 [109] "Disaggregated" refers to the choice to assess impacts in a variety of indicators or units, e.g., changes in agricultural yields and loss of biodiversity. By contrast, monetized CBA converts all impacts into a common unit (money), which is used to assess changes in social welfare.
Analysts have assessed global warming in relation to sustainable development. [110] Sustainable development considers how future generations might be affected by the actions of the current generation. In some areas, policies designed to address global warming may contribute positively towards other development objectives, for example abolishing fossil fuel subsidies would reduce air pollution and thus save lives. [111] [112] [113] Direct global fossil fuel subsidies reached $319 billion in 2017, and $5.2 trillion when indirect costs such as air pollution are priced in. [114] In other areas, the cost of global warming policies may divert resources away from other socially and environmentally beneficial investments (the opportunity costs of climate change policy). [111] [112]
The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to advance scientific knowledge about climate change caused by human activities. The World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) established the IPCC in 1988. The United Nations endorsed the creation of the IPCC later that year. It has a secretariat in Geneva, Switzerland, hosted by the WMO. It has 195 member states who govern the IPCC. The member states elect a bureau of scientists to serve through an assessment cycle. A cycle is usually six to seven years. The bureau selects experts to prepare IPCC reports. It draws the experts from nominations by governments and observer organisations. The IPCC has three working groups and a task force, which carry out its scientific work.
The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in the atmosphere. It was signed by 154 states at the United Nations Conference on Environment and Development (UNCED), informally known as the Earth Summit, held in Rio de Janeiro from 3 to 14 June 1992. Its original secretariat was in Geneva but relocated to Bonn in 1996. It entered into force on 21 March 1994.
Emissions trading is a market-based approach to controlling pollution by providing economic incentives for reducing the emissions of pollutants. The concept is also known as cap and trade (CAT) or emissions trading scheme (ETS). Carbon emission trading for CO2 and other greenhouse gases has been introduced in China, the European Union and other countries as a key tool for climate change mitigation. Other schemes include sulfur dioxide and other pollutants.
There is a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.
The IPCC Third Assessment Report (TAR), Climate Change 2001, is an assessment of available scientific and socio-economic information on climate change by the IPCC. Statements of the IPCC or information from the TAR were often used as a reference showing a scientific consensus on the subject of global warming. The Third Assessment Report (TAR) was completed in 2001 and consists of four reports, three of them from its Working Groups: Working Group I: The Scientific Basis; Working Group II: Impacts, Adaptation and Vulnerability; Working Group III: Mitigation; Synthesis Report. A number of the TAR's conclusions are given quantitative estimates of how probable it is that they are correct, e.g., greater than 66% probability of being correct. These are "Bayesian" probabilities, which are based on an expert assessment of all the available evidence.
The Second Assessment Report (SAR) of the Intergovernmental Panel on Climate Change (IPCC), published in 1995, is an assessment of the then available scientific and socio-economic information on climate change. The report was split into four parts: a synthesis to help interpret UNFCCC article 2, The Science of Climate Change, Impacts, Adaptations and Mitigation of Climate Change, Economic and Social Dimensions of Climate Change. Each of the last three parts was completed by a separate Working Group (WG), and each has a Summary for Policymakers (SPM) that represents a consensus of national representatives.
The Special Report on Emissions Scenarios (SRES) is a report by the Intergovernmental Panel on Climate Change (IPCC) that was published in 2000. The greenhouse gas emissions scenarios described in the Report have been used to make projections of possible future climate change. The SRES scenarios, as they are often called, were used in the IPCC Third Assessment Report (TAR), published in 2001, and in the IPCC Fourth Assessment Report (AR4), published in 2007. The SRES scenarios were designed to improve upon some aspects of the IS92 scenarios, which had been used in the earlier IPCC Second Assessment Report of 1995. The SRES scenarios are "baseline" scenarios, which means that they do not take into account any current or future measures to limit greenhouse gas (GHG) emissions.
Climate change mitigation is action to limit climate change by reducing emissions of greenhouse gases or removing those gases from the atmosphere. The recent rise in global average temperature is mostly caused by emissions from fossil fuels burning. Mitigation can reduce emissions by transitioning to sustainable energy sources, conserving energy, and increasing efficiency. In addition, CO2 can be removed from the atmosphere by enlarging forests, restoring wetlands and using other natural and technical processes, which are grouped together under the term of carbon sequestration.
Flexible mechanisms, also sometimes known as Flexibility Mechanisms or Kyoto Mechanisms, refers to emissions trading, the Clean Development Mechanism and Joint Implementation. These are mechanisms defined under the Kyoto Protocol intended to lower the overall costs of achieving its emissions targets. These mechanisms enable Parties to achieve emission reductions or to remove carbon from the atmosphere cost-effectively in other countries. While the cost of limiting emissions varies considerably from region to region, the benefit for the atmosphere is in principle the same, wherever the action is taken.
Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC) was published in 2007 and is the fourth in a series of reports intended to assess scientific, technical and socio-economic information concerning climate change, its potential effects, and options for adaptation and mitigation. The report is the largest and most detailed summary of the climate change situation ever undertaken, produced by thousands of authors, editors, and reviewers from dozens of countries, citing over 6,000 peer-reviewed scientific studies. People from over 130 countries contributed to the IPCC Fourth Assessment Report, which took six years to produce. Contributors to AR4 included more than 2,500 scientific expert reviewers, more than 800 contributing authors, and more than 450 lead authors.
The social cost of carbon (SCC) is the marginal cost of the impacts caused by emitting one extra tonne of carbon emissions at any point in time. The purpose of putting a price on a ton of emitted CO2 is to aid people in evaluating whether adjustments to curb climate change are justified. The social cost of carbon is a calculation focused on taking corrective measures on climate change which can be deemed a form of market failure. The Intergovernmental Panel on Climate Change suggested that a carbon price of $100/tCO2 could reduce global GHG emissions by at least half the 2019 level by 2030.
Carbon leakage occurs when there is an increase in greenhouse gas emissions in one country as a result of an emissions reduction by a second country with a strict climate policy.
Climate risk refers to risk assessments based on formal analysis of the consequences, likelihoods and responses to the impacts of climate change and how societal constraints shape adaptation options. Common approaches to risk assessment and risk management strategies based on natural hazards have been applied to climate change impacts although there are distinct differences. Based on a climate system that is no longer staying within a stationary range of extremes, climate change impacts are anticipated to increase for the coming decades despite mitigation efforts. Ongoing changes in the climate system complicates assessing risks. Applying current knowledge to understand climate risk is further complicated due to substantial differences in regional climate projections, expanding numbers of climate model results, and the need to select a useful set of future climate scenarios in their assessments.
The United Nations Intergovernmental Panel on Climate Change (IPCC) published a special report on Renewable Energy Sources and Climate Change Mitigation (SRREN) on May 9, 2011. The report developed under the leadership of Ottmar Edenhofer evaluates the global potential for using renewable energy to mitigate climate change. This IPCC special report provides broader coverage of renewable energy than was included in the IPCC's 2007 climate change assessment report, as well as stronger renewable energy policy coverage.
The Fifth Assessment Report (AR5) of the United Nations Intergovernmental Panel on Climate Change (IPCC) is the fifth in a series of such reports and was completed in 2014. As had been the case in the past, the outline of the AR5 was developed through a scoping process which involved climate change experts from all relevant disciplines and users of IPCC reports, in particular representatives from governments. Governments and organizations involved in the Fourth Report were asked to submit comments and observations in writing with the submissions analysed by the panel. Projections in AR5 are based on "Representative Concentration Pathways" (RCPs). The RCPs are consistent with a wide range of possible changes in future anthropogenic greenhouse gas emissions. Projected changes in global mean surface temperature and sea level are given in the main RCP article.
The economics of climate change mitigation is part of the economics of climate change related to climate change mitigation, that is actions that are designed to limit the amount of long-term climate change. Mitigation may be achieved through the reduction of greenhouse gas (GHG) emissions and the enhancement of sinks that absorb GHGs, for example forests.
Climate change scenarios or socioeconomic scenarios are projections of future greenhouse gas (GHG) emissions used by analysts to assess future vulnerability to climate change. Scenarios and pathways are created by scientists to survey any long term routes and explore the effectiveness of mitigation and helps us understand what the future may hold this will allow us to envision the future of human environment system. Producing scenarios requires estimates of future population levels, economic activity, the structure of governance, social values, and patterns of technological change. Economic and energy modelling can be used to analyze and quantify the effects of such drivers.
The economic impacts of climate change vary geographically and are difficult to forecast exactly. Researchers have warned that current economic forecasts may seriously underestimate the effects of climate change, and point to the need for new models that give a more accurate picture of potential damages. Nevertheless, one 2018 study found that potential global economic gains if countries implement mitigation strategies to comply with the 2 °C target set at the Paris Agreement are in the vicinity of US$17 trillion per year up to 2100 compared to a very high emission scenario. A study by the reinsurance company Swiss Reinsurance Company Ltd in 2021 estimated that global climate change is likely to reduce global economic output by 11-14%, or as much as $23 trillion annually by 2050, compared with global economic output without climate change. According to this study, the economies of wealthy countries like the United States would likely shrink by approximately 7% while some developing nations would be devastated, losing around 20% or in some cases 40% of the their economic output.
Co-benefits of climate change mitigation are the benefits related to mitigation measures which reduce greenhouse gas emissions or enhance carbon sinks.
The Sixth Assessment Report (AR6) of the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) is the sixth in a series of reports which assess scientific, technical, and socio-economic information concerning climate change. Three Working Groups covered the following topics: The Physical Science Basis (WGI); Impacts, Adaptation and Vulnerability (WGII); Mitigation of Climate Change (WGIII). Of these, the first study was published in 2021, the second report February 2022, and the third in April 2022. The final synthesis report was finished in March 2023.
Economic and population growth are among the most important drivers of increases in CO2 emissions from fossil fuel combustion...
Even in a scheme involving "equal burdens", most observers argue that a uniform carbon tax would not be fair because of the many differences outlined in Section 3.3 [of the IPCC report], notably differences in historical and current emissions and in current wealth and consequent priorities.