Uncertainties in predictions of climate change and sea level rise-a review

Abstract

The chronological development of the research methodologies on climate change and resultant sea level rise during the last two decades have been premeditated and it is found that the various assumed scenarios to apprehend the rise in global temperature have been grounded on lot of uncertainties. The real time data in climate change as well as sea level rise has been observed to be in variance from IPCC’s estimated predictions. The gradual transition on the concept of emission pathway scenarios considered in SRES (2000) from the beginning of millennium till present concept of Representative Concentration Pathways (RCPs) in AR5 of IPCC has been referred. The scenario concepts in SRES (2000), being about 20 years old have gradually been modified and the scientific community now prefer modelling climate change based on RCPs (Representative Concentration Pathways). RCPs do not represent detailed socio economic narratives or scenarios like that considered in SRES but pathways of radiative forcing. Radiative Forcing (RF) measures the capacity of a gas affecting the change in energy in the atmosphere due to GHG emissions. Unlike SRES, RCPs do not represent detailed socio-economic scenarios but Radiative Forcing, the capacity of a gas affecting the change in energy in the atmosphere due to GHG emissions. IPCC in its Fifth Assessment Report (AR5) considers four greenhouse gas concentration (not emissions) trajectories as Representative Concentration Pathways (RCPs) viz. RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5, considering possible range of radiative forcing values in 2100. However, in AR6 of IPCC, expected to come out in 2022, the scenarios are again likely to change during advent of CMIP6 and the variations in contributing factors in the form of Shared Socio-economic Pathways (SSPs). Particularly at present the melting of ice sheets at Antarctica and Greenland reportedly is going to a stage of no return and according to some school of thought of scientists self-sustained melting of the permafrost will linger. It is already proclaimed that even in a situation if all anthropogenic emission of GHGs is immediately stopped the self-sustained melting will continue. The models so far being based on numerical and probabilistic approaches are all drastically expected to undergo abrupt change because of the current icesheet dynamics at Antarctica and Greenland. Giving due weightage to deep uncertainty in sociopolitical and economic changes amongst nations, as well as the ice dynamics in present accelerated warming situation, while the importance of usability of model hierarchy for the complex science of climate change is stressed upon, the debate on uncertainty is acknowledged. The query remains whether the research on sea level rise is likely to take a new turn in the coming decades. Multidisciplinary approach to research with minimum uncertainty in a more precise and finer manner is called for.