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Why the IPCC Scientific Assessment Should be a Major Driver in Climate Negotiations

By Dr R.K. Pachauri, Chairman, Intergovernmental Panel on Climate Change (IPCC)

Director-General, The Energy & Resources Institute (TERI)


The COP process has moved along with significant inputs from the Intergovernmental Panel on Climate Change (IPCC).

The very First Assessment Report (FAR) of the IPCC which came out in 1990 was particularly important in providing a scientific basis for the development of the United Nations Framework Convention on Climate Change (UNFCCC). Similarly, the Kyoto Protocol which was completed as a document in 1997 benefitted greatly from the Second Assessment Report (SAR) of the IPCC which came out in 1995/96. The Third Assessment Report (TAR) for the first time provided adequate focus on adaptation measures. Finally the Fourth Assessment Report (AR4) provided a substantial level of evidence on how human actions are responsible to a large extent for changes in the climate system taking place worldwide. It was in recognition of this entire record of the IPCC that the organisation was awarded the Nobel Peace Prize in 2007. When I was privileged to deliver the acceptance speech on behalf of the IPCC I highlighted three important realities.

1)  The power and promise of collective scientific endeavour, which, as demonstrated by the IPCC, can reach across national boundaries and political

Rajendra K. Pachauri, Chairman of the IPCC
Rajendra K. Pachauri, Chairman of the IPCC

differences in the pursuit of objectives defining the larger good of human society.

2)  The importance of the role of knowledge in shaping public policy and guiding global affairs for the sustainable development of human society.

3)  An acknowledgement of the threats to stability and human security inherent in the impacts of a changing climate and, therefore, the need for developing an effective rationale for timely and adequate action to avoid such threats in the future.

It is vitally important that COP19 in Warsaw should benefit from the scientific assessments provided by the IPCC so far, and more importantly the findings of the Working Group I report which is the first major output of the Fifth Assessment Report (AR5).Some findings of the AR5 Working Group I (WG I) report are particularly relevant in creating an understanding of actions that need to be taken and creating the level of ambition by which the challenge of climate change can be met effectively and equitably. Much like the AR4, this report has stated that warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases (GHGs) have increased. What is particularly significant is that each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years. For the first time the IPCC has also been able to quantify the distribution of warming between land areas and the oceans. Hence, it was stated that ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90 per cent of the energy accumulated between 1971 and 2010. It is virtually certain that the upper ocean (0−700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971. Sea level rise is a function of thermal expansion of the oceans and melting of the bodies of ice across the planet. In this context, it is important to note that over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent. Consequently, the rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901–2010, global mean sea level rose by 0.19 (0.17 to 0.21) m.

Human actions have brought about a major increase in the concentration of GHGs in the earth’s atmosphere, in relation to long term trends. It can be said that the atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40 per cent since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30 per cent of the emitted anthropogenic carbon dioxide, causing ocean acidification.

While making projections of the future the AR5 WG I report has found that global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform. The effect of climate change on Arctic sea ice will continue to be serious. Hence, it was found that it is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease. Global mean sea level will continue to rise as a result both of the melting of ice across the global and thermal expansion of the ocean. Global mean sea level rise for 2081−2100 relative to 1986–2005 will likely be in the ranges of 0.26 to 0.55 m for RCP2.6, 0.32 to 0.63 m for RCP4.5, 0.33 to 0.63 m for RCP6.0, and 0.45 to 0.82 m for RCP8.5. For RCP8.5, the rise by the year 2100 is 0.52 to 0.98 m, with a rate during 2081–2100 of 8 to16 mm yr–1. These ranges are derived from CMIP5 climate projections in combination with process-based models and literature assessment of glacier and ice sheet contributions.

In order to make the most effective use of the scientific assessment provided by the IPCC, a detailed exposition of the major findings of the IPCC reports produced thus far would assist the process of the COP effectively. It would be relevant to mention that since the publication of the AR4 two special reports have also been brought out by the IPCC, namely the Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) and the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). In the first of these reports two important facts were put forward on the basis of substantial evidence and assessment of past trends. Firstly, in a number of applications renewable energy technologies were already competing effectively with conventional sources. In the second report, not only were certain extreme events found to have increased in frequency and intensity but projections for the future clearly indicated that it is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur in the 21st century at the global scale. It was also found very likely that the length, frequency, and/or intensity of warm spells or heat waves will increase over most land areas. At the same time it was also found likely that the frequency of heavy precipitation or the proportion of the total rain fall very heavy falls will increase in the 21st century over many areas of the globe.

Essentially, in each forthcoming COP leading up to COP21, it would be important for the agenda to include a clear understanding of outcomes that science projects would accrue if the world does not act on a timely and adequate basis as well as look at the attractiveness and comprehensive benefits of taking action. In other words it is important that a higher level of attention to the scientific assessment provided by the IPCC be one of the major drivers of negotiations in the coming two years leading upto the COP21 in 2015.




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