Science in Society Archive

IPCC Final Climate Warning Before Bali

Evidence for global warming unequivocal and most likely due to human activities, but there is high confidence for effective adaptation as well as high agreement and much evidence of substantial economic potential for mitigation; the cost of fighting global warming at the most stringent level will cost no more than 0.12 percent of global GDP a year up to 2030. Dr. Mae-Wan Ho

The latest IPCC (Intergovernmental Panel on Climate Change) Synthesis Report [1], released 17 November 2007, presents “a stark and dire warning about climate change”[2], and prepares the ground for the December meetings of the UN Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol in Bali. The developed countries are expected to make further commitments to reduce their greenhouse gas (GHG) emissions beyond the Kyoto Protocol’s 2008-2012 first commitment period.

The week in Valencia was described by Third World Network’s director Martin Khor as a “long and difficult meeting” [2]; especially controversial was the section on long term perspectives and the five “reasons for concern” in the Summary for Policy Makers [1].

The Synthesis Report, adopted after extensive comments by governments and several amendments, integrates and condenses a vast body of scientific literature from three working group reports released earlier in the year: The Physical Science Basis; Impacts, Adaptation and Vulnerability; and Mitigation of Climate Change.

Warming of global climate “unequivocal” and accelerating

“Warming of the climate system is unequivocal”, so said Dr. Rajenda Pachauri, Chair of the Interngovernmental Panel on Climate Change, in his presentation to the press [3]. Measurements show air and ocean temperatures increasing, global sea level rising, snow and ice reducing, increase in heavy rains, droughts, and heat waves [4].

Eleven of the past twelve years are among the warmest on record since 1850. The last time that the earth warmed to such an extent was at least 1 300 years ago. But the last time the polar regions were significantly warmer than the present for an extended period was 125 000 years ago, and it led to a 4 to 6 m rise in sea level.

Widespread decreases in glaciers and ice caps have contributed to sea level rise. New data since the last assessment report in 2001 show losses from the ice sheets of Greenland and Antarctica have very likely contributed to sea level rise over 1993 to 2003. Global sea level rose at an average rate of 1.8 mm per year between 1961 and 2003, but the rate accelerated in the period between 1993 and 2003 to about 3.1 mm per year.

 “At continental, regional and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.”

Average arctic temperatures increased at almost twice the global average rate in the past 100 years. Satellite data since 1978 show that annual average arctic sea ice extent has shrunk by 2.7 percent per decade, with larger decreases in summer of 7.5 to 9.8 percent per decade. Temperatures at the top of the permafrost layer have generally increased since the 1980s in the Arctic by up to 3 °C. The maximum area covered by seasonally frozen ground has decreased by about 7 percent in Northern Hemisphere since 1900, with a decrease in spring of up to 15 percent.

Long-term trends in rainfall from 1900 to 2005 have been observed over many large regions: significant increase in eastern parts of North and South America, northern Europe and northern and central Asia; drying in the Sahel, the Mediterranean, southern Africa and parts of southern Asia.

Precipitation is highly variable spatially and temporally. Globally, the area affected by drought has also increased since the 1970s.

There have been changes in precipitation and evaporation over the oceans with freshening of mid- and high-latitude waters together with increased salinity in low-latitude waters.

Mid latitude westerly winds have strengthened in both hemispheres since the 1960s. There have been more intense and longer droughts over wider areas since the 1970s, particularly in the topics and subtropics.

The frequency of heavy precipitation events has increased over most land areas, consistent with warming and observed increases of atmospheric water vapour. There have been widespread changes in extreme temperatures over the past 50 years. Cold days, cold nights and frosts less frequent, while hot days, hot nights and heat waves have become more frequent.

There is evidence of “an increase in intense tropical cyclone activity in the North Atlantic since about 1970, with limited evidence of increases elsewhere.”

The text on cyclones was subject to intense and protracted discussion, as the US had proposed introducing a number of qualifications to the original [2], probably having in mind Hurricane Katrina that hit the country in 2006, while Cyclone Sidr has just devastated Bangladesh in November 2007, with an estimated 900 000 families affected and a death toll of more than 10 000 and rising [5].

Human activities are the main cause of global warming

The Summary of the IPPC Synthesis Report [1] expresses “very high confidence” that the net effect of human activities since 1970 has caused global warming. “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” This is an advance since the conclusion of the previous Third Assessment Report that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”.

“Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns..” [4].

Results simulated by climate models using natural and anthropogenic emissions for the period 1906 to 2005 indeed show that anthropogenic emissions are responsible for temperature increases over both landmasses and the ocean.

Global increase in CO2 concentrations is due primarily to fossil fuel use, with change in land use also contributing a significant amount. Increase in the other major greenhouse gases methane and nitrous oxide are primarily due to agriculture. CO2 has increased from a pre-industrial 280 to 379 ppm (parts per million) in 2005. The annual CO2 growth rate was larger during the past ten years at 1.9 ppm per year than it has been since the beginning of continuous direct measurements (1960-2005 average 1.4 ppm per year).

The annual fossil CO2 emissions increased from an average of 6.4 Gt per year in the 1990s to 7.2 Gt per year in 2000-2005. CO2 emissions association with land-use change is estimated to be 1.6 per year over the 1990s. Global methane in the atmosphere has increased from the pre-industrial value of about 715 to 1732 ppb (parts per billion) in the early 1990s and 1774 ppb in 2005, exceeding by far the natural range of the past 650 000 years (320 to 790 ppb). Growth rate has declined since the early 1990s. Global nitrous oxide increased from pre-industrial value of about 270 to 319 ppb in 2005, its growth rate approx constant since 1980, and more than a third is due to agriculture.

Dire impacts of climate change projected

Various IPCC scenarios (see Box 1) [4] project emissions increases of between 25 and 90 percent between 2000 and 2030 and beyond. Continued emissions at or above the current rate would cause further warming and induce many changes in the present century  “very likely” to be larger than those observed during the past century.

Box 1

The IPCC Special Report on Emission Scenarios (SREs)

The SRES scenarios are different models for predicting emissions, global temperatures and other aspects of global warming under different storylines, they do not include additional climate initiatives, which means that no scenarios are included that explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol.

A1 scenario family describes a future world of very rapid economic growth, with global population peaking in mid-century and declining thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups distinguished by their technological emphasis: fossil-intensive (A1FI), non-fossil energy sources (A1T) or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

A2 scenario family describes a very heterogeneous world. The underlying theme is self-

reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other scenarios.

B1 scenario family describes a convergent world with the same global population, that

peaks in mid-century and declines thereafter, as in the A1 scenario, but with rapid change in economic structures toward a service and information economy,  reductions in material intensity and the introduction of clean and resource-efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

B2 scenario family describes a world that emphasizes local solutions to economic, social and environmental sustainability, with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

Warming is inevitable [4]. For the next two decades, a warming of about 0.2°C per decade is projected for a range of emission scenarios. “Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1 °C per decade would be expected.” The projected temperature rise by the end of this century is between 1.1 and 6.4 °C over all scenarios.

On the most stringent goal set to combat climate change, emissions of GHG would have to peak by 2015 to limit temperature rises to 2.0 - 2.4 °C.

There is higher confidence than in previous IPCC reports “in projected patterns of warming and other regional-scale features.” This suggests an increase in the frequency of hot extremes, heat waves and heavy rainfall. Rainfall is also very likely to increase in the high latitudes and likely to decrease in most subtropical regions. Tropical cyclones are likely to become more intense. There is “high confidence” that many semi-arid areas, such as the Mediterranean basin, western United States, southern Africa and northern Brazil, will suffer a decrease in water resources.

Specific projections for different regions are as follow [1].

  • In Africa, between 75 and 250 million will be exposed to increased water stress, yields from rain-fed agriculture will fall by up to 50 percent
  • In Asia, freshwater availability will decrease, coastal areas will be at greater risk from increased flooding, and climate change will compound pressures on natural resources and public health;
  • In Latin America, there will be significant loss of biodiversity through species extinction. The productivity of some important crops will decline, with increase in the number of people at risk of hunger. And water available for human consumption, agriculture and energy generation is likely to be significantly affected.
  • Small Islands are expected to face flooding, storm surges, erosion and other coastal hazards, threatening vital infrastructure, settlements and livelihoods.  The erosion of beaches and coral bleaching is expected to affect local resources, and by mid-century, climate change is expected to reduce water resources in many small islands.

Global warming could also lead to some impacts that are “abrupt or irreversible”. Approximately 20-30 percent of species are likely to be at increased risk of extinction if warming exceeds 1.5 to 2.5 °C, and after 3.5 °C, models predict extinctions of 40-70 percent of species.

Although the different IPPC scenarios predict sea level rise between 18 and 59 cm by the end of this century, the Synthesis Report Summary [1] states that more rapid sea level rise over century time scales “cannot be excluded”. Complete elimination of the Greenland ice sheet could cause a seven-metre sea level rise. None of the IPPC scenarios include climate-carbon feedbacks, nor the full effects of changes in ice sheet flows. Notably, the Report does  “not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise.”

Adaptation and mitigation options

The Summary [1] states that “a wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to climate change.” It alludes to “barriers, limits and costs” to adaptation “not fully understood”, and says that the capacity to adapt is intimately connected to social and economic development, which is unevenly distributed across and within societies.

Vulnerability to climate change can be exacerbated by other stresses, for example, “current climate hazards, poverty and unequal access to resources, food insecurity, trends in economic globalisation, conflict and incidence of diseases such as HIV/AIDS.”

There is high confidence that there are viable adaptation options that can be implemented in some sectors at low cost, and/or with high benefit-cost ratios.”

Many obvious adaptation technologies are mentioned, such as rainwater harvesting, improved land management, erosion control and soil protection through tree planting; creation of marshlands/wetlands as buffer against sea level rise and flooding, and heat-health action plans.

The Summary notes that there is “high agreement and much evidence of substantial economic potential for mitigation of global GHG emissions over the coming decades that could offset the projected growth of global emissions or reduce emissions below current levels.”

Examples of mitigation technologies likely to prove controversial are nuclear power, carbon dioxide capture and storage, and biofuels. Astonishingly, organic agriculture is not mentioned among the mitigation technologies.

It states that no single technology can provide all of the mitigation potential in any sector. “The economic mitigation potential, which is generally greater than the market mitigation potential, can only be achieved when adequate polices are in place and barriers removed.” The economic potentials are based on the market price of CO2 [6] and have a ring of unreality to them. For one thing, they are based on outdated prices for fossil fuels (crude oil at US$ 25/ barrel), and have not factored in the strong demand for oil from China in recent years (see later).

It mentions a wide variety of polices and instruments available to governments to create the incentives for mitigation action: higher taxes on emissions, regulations, tradeable permits and research.

Perhaps the most important message is that the costs of fighting global warming will range from less than 0.12 percent of Global GDP per year for the most stringent scenarios (stabilization of atmospheric GHG at 445-535 ppm CO2e) until 2030 to less than 0.06 percent for a less tough goal (590-710 ppm CO2e). In the most costly cases, a loss of GPD by 2030 is less than 3 percent.

Most controversial long-term perspectives

The discussion on the long-term perspective was the most controversial, given its particular importance for framing the findings in the rest of the report, and hence its influence it is likely to have at the UNFCCC negotiations [2]. A Contact Group was formed early in the week in Valencia to resolve this issue, and discussions were mainly addressed through the Contact Group.

The objective of the UNFCCC is “stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system”. Such a level is to be achieved “within a time-frame sufficient to allow ecosystems to adapt naturally to climate change”.

The Summary [1] concludes that determining what constitutes “dangerous anthropogenic interference” involves value judgements by policy-makers. But science can support informed decisions on this issue, by providing criteria for judging which vulnerabilities might be labelled “key”.

The bone of contention at the Valencia meeting was the five “reasons for concern”: risks to unique and threatened systems, risks of extreme weather events, distribution of impacts and vulnerabilities, aggregate impacts, and risks of large-scale singularities - which are considered a viable framework for considering key vulnerabilities (see Box 2).

Box 2

IPCC’s five “reasons for concern” identifies key vulnerabilities for UNFCCC negotiations [2]

Risks to unique and threatened systems

There is “new and stronger evidence of observed impacts of climate change on unique and vulnerable systems (such as polar and high mountain communities and ecosystems) with increasing levels of adverse impacts as temperatures increase further”.

An increasing risk of species extinction and coral reef damage is projected with higher confidence than in the last Assessment Report. There is increased confidence that a 1-2 oC increase in global mean temperature above 1990 levels (about 1.5-2.5oC above pre-industrial) poses significant risks to many unique and threatened systems including many biodiversity hotspots.

Increases in sea surface temperature of about 1-3 oC are expected to result in more frequent coral bleaching events and widespread coral mortality. Increasing vulnerability of indigenous communities in the Arctic and small island communities is also projected.

Risks of extreme weather events

There is “higher confidence in the projected increases in droughts, heatwaves, and floods as well as their adverse impacts” and that there are higher levels of vulnerabilities than that concluded in the last Assessment Report.

Distribution of impacts and vulnerabilities

According to the Summary, “there are sharp differences across regions and those in the weakest economic position are often the most vulnerable to climate change”.

There is also increasing evidence of greater vulnerability of specific groups such as the poor and elderly in developing and developed countries. There is increased evidence that low-latitude and less-developed areas generally face greater risk, for example in dry areas and mega-deltas.

Aggregate impacts

Initial net market-based benefits from climate change are projected in the Summary to peak at a lower magnitude of warming, while damages would be higher for larger magnitudes of warming. The net costs of impacts of increased warming are projected to increase over time.

Risks of large-scale singularities

The Summary states that “there is high confidence that global warming over many centuries would lead to a sea level rise contribution from thermal expansion alone which is projected to be much larger than observed over the 20th century, with loss of coastal area and associated impacts”.

The US had proposed that the section and the five reasons for concern should be deleted; but in the end, they remained after extensive discussion and amendment. This section helps to actively link the conclusion in the Summary with the UNFCCC’s goal of avoiding “dangerous anthropogenic interference with the climate system”. 

According to the Summary [1], “key vulnerabilities” can be identified based on a number of criteria in the literature including magnitude, timing, persistence/reversibility, potential for adaptation, distributional aspects, likelihood and ‘importance’ of the impacts. These may be associated with many climate sensitive systems such as food supply, infrastructure, health, water resources, coastal systems, ecosystems, global biogeochemical cycles, ice sheets, and modes of oceanic and atmospheric circulation.

The reasons for concern were already reflected in the IPCC Third Assessment Report, but are considered to be stronger now in the current IPCC Fourth Assessment Report, as many of the risks are identified with higher confidence and some risks are projected to be larger or to occur at lower increases of temperature. In addition, the understanding about the relationship between impacts and vulnerability has improved.

The Summary [1] reflected the hard fought interest of the countries that discussed and finalised the document, says Martin Khor [2]. The Fourth Assessment Report of the IPCC and its Summary will be the scientific basis on which important policy decisions for future emissions reduction and other commitments will be taken by the UNFCCC. 

The US is not a Party to the Kyoto Protocol and is therefore not bound to reduce its greenhouse gas emissions, although it is still the largest (absolute and per capita) emitter in the world. The US was very active during the Valencia meetings and had made extensive written proposals to essentially weaken the document, such as by downplaying the likelihood of future global warming and by weakening the links between the causes and effects of climate change.  Part of the US’ submissions seemed to be aimed at attempting to divert the focus from the developed countries’ responsibility onto other developing countries with large emissions (but much smaller per capita emissions).

Saudi Arabia often sought to introduce language on “spillover effects”, meaning the effects of climate change on countries whose economies are dependent on oil, which may suffer declining demand for oil as countries shift towards energy efficiency and renewable energies.

The majority of countries were mainly concerned with finalising a document that reflected the findings and conclusions of the IPCC scientists.  Of the developing countries, the small island states were among the main advocates for conclusions supporting strong action.

The IPCC reports are consensus scientific documents that consist of mainstream climate change findings, and have been widely criticized as being on the conservative side.

As pointed out in The New York Times [7], the process of producing an assessment report takes five years of study and writing and cannot take into account the very latest data on climate change or economic trends, which show larger than predicted development and energy use in China.

Gernot Klepper at the Kiel Institute for World Economy in Germany points out that the world is already at or above the worst-case scenario in terms of emissions. In 2006, 8.5 Gt of C (31.17 Gt CO2) were released into the atmosphere from fossil fuels, which is almost identical to the IPCC’s worst-case prediction for that year.

The same goes for the future melting of ice sheets in Greenland and western Antarctica. In earlier reports, the panel’s scientists acknowledged that their computer models were poor at such predictions, and did not reflect the rapid melting recently observed. If these areas melt entirely, sea level would rise by 40 feet (12.2 metres). There is now evidence this could happen much faster, perhaps over centuries instead of millennia.

Another thread of discussion that will be an important component in the UNFCCC negotiations is the issue of technology and financing for mitigation and adaptation, and the barriers to developing countries in successfully realizing them. The Summary [1] acknowledges these barriers but does not specify them and constantly suggests that they are “not fully understood”.

But if the cost of fighting climate change through combined adaptation and mitigation to keep atmospheric CO2 at the lowest levels is as cheap as 0.12 percent of global GDP per year as estimated [1], then these unspecified barriers could hardly be insurmountable. That’s perhaps the best message to take forward to Bali.

Article first published 03/12/07


  1. Summary for Policymakers of the Synthesis Report of the IPCC Fourth Assessment Report, Draft copy 16 November 2007, Subject to final copyedit,
  2. The IPCC Synthesis Report and the Valencia Meeting. A Report of the Third World Network, 27 November 2007,
  3. IPCC Fourth Assessment Report, Dr. R. K. Pachauri, Chair of the Intergovernmental Panel on Climate Change, Press Presentation, 27th Session of the Intergovernmental Panel on Climate Change, Valencia, 12-17 November 2007,
  4. IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M and Miller HL. Eds.) Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007.
  5. "Bangladesh cyclone death toll hits 15 000" , Peter Foster,, 21 November 2007,
  6. Metz B, Davidson OR, Bosch PR, Dave R, Meyer LA. (eds.).Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007.
  7. "U.N. Report descrbies risks of inaction on climate change" Elisabeth Rosenthal 17 November 2007, The New York Times,

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