Results of Second National Climate Change Study Consistent with the Intergovernmental Panel on Climate Change's 5th Assessment Report in Projecting Global Sea-Level Rise, Higher Temperatures and More Extreme Rainfall in the Region

Meteorological Service Singapore’s (MSS) Centre for Climate Research Singapore (CCRS) has released the findings for Phase 1 of the Second National Climate Change Study at a meeting of the Climate Science Experts Network^[1]. The outcomes of the new Singapore study are consistent with those of the Inter-governmental Panel on Climate Change (IPCC) 5^th Assessment Report (AR5) which projects sea level rises globally, as well as higher temperatures and more extreme rainfall for Singapore and the surrounding region. The details are outlined in paragraphs 5-11 below.

Background of Phase 1 of the 2^nd National Climate Change Study

Under the auspices of the Inter-Ministerial Committee on Climate Change (IMCCC), the National Environment Agency (NEA) and in collaboration with the Met Office Hadley Centre in the United Kingdom commissioned Phase 1 of the 2^nd National Climate Change Study, which aimed to provide projections of changes in the main climate variables of interest to Singapore. The key highlight of this report was the use of high resolution climate models to project regional climate and sea level changes with finer spatial detail for the 21st century over the region, centred on Singapore. The study was completed early this year.

Phase 2 of the study, which started in end 2014, is making use of the projections from Phase 1 to examine the climate change impacts on areas such as water resources and drainage, biodiversity and greenery, network infrastructure and building infrastructure. This in turn will guide Government agencies in their planning and will serve to shape Singapore’s climate change resilience plans. Key findings from Phase 2 can be expected by end 2015.

Phase 1 of the study makes use of the same global climate model projections that contributed to many of the findings of the physical science component of the AR5 published in 2013 (Please refer to Annex A for details of the IPCC, working groups and the assessment reports). A carefully chosen sub-set of the models for two future trajectories of greenhouse gas concentrations in the atmosphere was downscaled to a higher resolution of 12 km for the Southeast Asian region. The first trajectory (RCP8.5)^[2] is related to a ‘business as usual' scenario in which we continue to use fossil fuels with no mitigation and thus results in very high greenhouse gas emissions that continue to increase throughout the 21st century. The second trajectory (RCP4.5) assumes future action to control emissions, which peaks in mid-century and then declines. The results from the downscaled projections with these two scenarios are the basis for the study’s findings^[3].

Findings on Temperature

For the period of 2070 – 2099 (relative to 1980-2009), the study projects that average surface temperatures across Singapore will increase by 1.4°C – 2.7°C under the RCP4.5 greenhouse gas trajectory and by 2.9°C – 4.6°C for RCP8.5.

The findings imply that the unusually warm temperatures Singapore encounters occasionally could become the norm in the future and that days with ‘record’ temperatures above those experienced historically will become more frequent. Due to the high levels of humidity in Singapore, these projected rises in temperature will lead to increasing thermal discomfort and heat stress for those working outdoors.

The high levels of temperature increase under the RCP8.5 scenario will be realised only if there is no global mitigation action to reduce greenhouse emissions.

Findings on Rainfall

The projections from most models show an increasing trend, particularly during the wetter season, in the intensity and frequency of heavy rainfall events over Singapore.

For seasonal average rainfall, the contrast between the wetter and drier months is projected to become more pronounced, especially for the RCP8.5 trajectory and by the end of the century. The study projects an upward trend in seasonal mean rainfall during the wet season of November to January, as well as greater dryness during months that are already relatively drier in the current climate (February and June to September).

Findings on Sea Level

For the period of 2070 – 2099 (relative to 1980-2009), the study projects a mean sea level rise of 0.25m – 0.60m under the RCP4.5 greenhouse gas trajectory and 0.35m – 0.76m for RCP8.5. Under the ‘high-emissions’ RCP8.5 greenhouse gas trajectory, the study projects a total rise of 0.45m – 1.02m by the year 2100.

The study projects no consistent future changes in the amplitude of extreme sea level events, such as as wind driven coastal storm surges and high waves. These events will, however, occur against a backdrop of increased mean sea levels.

Staying Resilient In The Face Of Climate Change

The effects of climate change operate in the long term, but the Government is taking a proactive approach to address its potential impact. The Inter-Ministerial Committee on Climate Change (IMCCC) was established in 2007 to enhance Whole-of-Government coordination on climate change policies. The Resilience Working Group (RWG), an inter-agency platform under the IMCCC, studies Singapore’s vulnerability to the effects of climate change and recommends long-term plans that ensure the nation’s adaptation to future environmental changes. The findings from this study will provide the basis by which we continually develop long-term infrastructure adaptation plans to appropriately address the effects of climate change on Singapore’s physical environment. The Government has also set aside at least $50 million for climate resilience related studies to support Singapore’s adaptation planning efforts.

Report on Phase 1 of the Second National Climate Change Study

A Stakeholder Report which provides a summary of the study’s methodologies and findings is now available on the CCRS website (http://ccrs.weather.gov.sg/). The Report is intended for those who will be actively engaged in the use of the projections for impact studies and adaptation planning.

Annex A: Overview of the Intergovernmental Panel on Climate Change

Infographic: Climate change in Singapore

^[1] The Climate Science Experts Network (CSEN) was launched in January 2012 by the Meteorological Service Singapore (MSS) and the Ministry of the Environment and Water Resources (MEWR). CSEN is a technical and sharing platform for Singapore-based experts in the physical science of climate change, bringing together academics from different disciplines to forge a collaborative framework.

^[2]‘Representative Concentration Pathway’ (RCP) 8.5. In AR5, a selection of four greenhouse gas concentration pathways were used as the input to drive climate models: RCPs 2.6, 4.5, 6.0 and 8.5. The higher numbers indicate greater projected imbalances in the climate by the year 2100.

^[3]The Representative Concentration Pathways (RCPs) are labelled by the change in the approximate total radiative forcing in the year 2100 relative to 1750, due to the enhanced greenhouse effect associated each pathways. For example, under RCP4.5 this change is 4.5 Wm^-2.

Source: National Environment Agency