As a result of human influence, the earth will warm by more than 2°C within this century, and the world will see more extreme weather events like drought and flooding, the Intergovernmental Panel on Climate Change (IPCC)’s latest report suggests.
The report's findings were released on Aug. 9, and is the first instalment out of three major reports that make up the IPCC's Sixth Assessment Report (AR6).
The Centre for Climate Research Singapore (CCRS), a research arm of the Meteorological Service Singapore (MSS) under National Environment Agency (NEA), is assessing the relevance of the results in the Singapore context.
AR6's key findings are guided by five emissions scenarios called Shared Socioeconomic Pathways (SSPs).
SSPs offer five pathways the world can take, with SSP1-1.9 being a low emission scenario where the world shifts to an ideal sustainable path and climate mitigation measures are adopted.
Meanwhile, SSP5-8.5 is the worst case emission scenario where economic development continues with the use of fossil fuels, including the business-as-usual scenario.
Global temperature to increase in all scenarios
According to the report, under the first four scenarios, the average global surface temperature rise is estimated to cross the 1.5°C mark in the early 2030s.
However, in the highest emission scenario SSP5-8.5, average global surface temperature rise will cross the 1.5°C mark by 2030.
In the decades to come, between the years 2081 and 2100, average surface temperatures across the world will increase by at least 1.3°C to 2.4°C under the low emission scenario of SSP1-2.6.
Average surface temperatures will increase by 3.3°C to 5.7°C for the highest emission scenario.
The latest report also reiterated that heavy precipitation events will intensify and become more frequent with each additional degree of warming.
Southeast Asia, in particular, will experience an increase in mean monsoon precipitation, IPCC reported. Flooding will be more frequent during extreme rainfalls when the ground cannot absorb the rain water effectively or drainage systems get overwhelmed.
Earlier in July, Henan in China saw massive floods that caused a number of deaths and halted transport services in the city of Zhengzhou.
It was described by local meteorologists as the heaviest rain in 1,000 years.
In the past few weeks, extraordinary rainfalls were experienced in Germany and India too.
Rising sea levels
The changes in mean sea level revealed by the latest report are not much different from the results in the earlier IPCC Fifth Assessment Report, which was published in 2014.
Under the low emission scenario SSP1-2.6, global mean sea levels are projected to rise by 0.32m to 0.62m.
Sea levels are projected to rise by 0.63m to 1.01m under the highest emission scenario.
This is because sea level rise is a long and drawn out process. Additionally, sea level change is not uniform globally, and different regions and countries may see varying changes in sea level that differ from the global mean.
What does this mean for Singapore?
Singapore, being a highly urbanised city, has experienced a stronger global warming trend over the past several decades.
Singapore will thus feel the effect of elevated temperatures in the near future, according to the joint media release by MSS and the Ministry of Sustainability and the Environment (MSE).
At this point in time, however, it is uncertain how rainfall in Singapore will be affected by global warming.
Singapore’s year-to-year rainfall is highly variable. However, the average annual rainfall for Singapore since 1980 has increased at an average rate of around 70mm per decade.
The intensity and frequency of heavy rainfall events have also increased over the past few decades up until 2012, but these trends were modulated by strong El Niño conditions in 2015 and 2016.
New study on how climate change affects Singapore to be completed in 2022
MSS said it will continue to study the evolving science around climate change attribution along with the impact of climate change on Singapore's weather.
A regional "SINGV" model has been developed by CCRS and the UK meteorological office which enables MSS to provide km-scale operational weather forecasts for Singapore and the region. This model which is more robust and accurate for our region will be used in the upcoming Third National Climate Change Study to inform Singapore's adaption plans in view of the latest IPCC findings.
The CCRS will also continue to study sea level rise in Singapore in greater detail under the National Sea Level Programme.
Third National Climate Change Study for Singapore is expected to be completed by the end of 2022.
Report provides more certainty about global warming
In response to a question from the media on how the report would be relatable to the layperson, a CCRS spokesperson said that the latest findings from AR6 should provide an "increased confidence" in what scientists are saying about climate change and a greater certainty in "what the signals [for global warming] might be".
Another CCRS spokesperson added that while Singapore's government has accepted the baseline of understanding climate change "for quite a while" and what they are doing is based on "solid science", some countries are still "struggling" to accept that they have to act on climate change.
Getting back to below 1.5°C increase
Going past a temperature increase of 1.5°C will likely trigger tipping points in the earth's system that could lead to irreversible changes.
These tipping points involve a variety of large-scale events, such as the loss of the Amazon rainforest (a huge carbon sink) or the melting of the West Antarctica ice sheet (which would cause 3m of sea-level rise).
However, the IPCC AR6 does not provide in-depth review on "tipping points" as "the science is still very much in its infancy on the understanding of tipping points," a CCRS spokesperson told the media.
Tipping points are likely to be excluded from the IPCC's Seventh Assessment Report (AR7) too even though there could be a special report on tipping points to be published before the release of AR7.
A CCRS spokesperson emphasised that moving forward, it is important to figure out how to reduce temperature rise to less than 1.5°C, instead of giving up or adopting a blasé approach.
While all AR6 scenarios suggest that the global mean surface temperature increase will cross the 1.5°C mark sometime in 2030s, it is still possible to limit warming at a later stage under low emission scenarios (SSP1-2.6), which represent mitigation pathways compatible with a 1.5°C and 2°C warming limit.
MSE said that Singapore is committed to play our part and will press on with efforts to mitigate and adapt to the effects of climate change.
Top photo by Zheng Zhangxin