On the eve of the United Nations climate summit starting on Monday, which aims to spur action on climate change, a new report by leading scientists warned that the 2015-2019 period is set to be the warmest five years on record.
The United in Science report compiles the latest information about climate change from leading science experts in cooperation with the World Meteorological Organisation.
It claims that accelerating climate impacts from melting ice caps to sea-level rises and extreme weather were to blame for the record as the global average temperature increased by 1.1°C above pre-industrial (1850-1900) times and 0.2°C warmer than 2011-2015.
"For the four year period, average temperatures were the highest on record for large areas of the United States, eastern parts of South American, most of Europe and the Middle East, northern Eurasia, Australia, and areas of Africa south of the Sahara," said the report, adding that July 2019 was the hottest month on record globally.
It also noted that greenhouse gas concentrations in the atmosphere have increased to record levels and will lead to catastrophic global warming if nothing is done to stop it.
“Climate change causes and impacts are increasing rather than slowing down,” said WMO Secretary-General Petteri Taalas, who is co-chair of the Science Advisory Group of the UN Climate Summit.
The report, which will be presented to world leaders at the climate summit, explained the grim results of some of climate change biggest impacts.
Rise in sea level
Between May 2014 and 2019, sea-level rose at a rate 5 mm per year, compared to 4 mm/year in the 2007-2016 period and 3.2 mm/year since 1993. One of the key factors was the rapidity of melting ice sheets from world glaciers in the last couple of years as well as the rapid rate of ocean warming.
Shrinking amount of ice
Arctic summer sea-ice extent —the area of sea with a specified amount of ice—has declined at a rate of approximately 12% per decade during 1979-2018. The four lowest values for winter sea-ice extent occurred between 2015 and 2019.
Overall, the amount of ice lost annually from the Antarctic ice sheet increased at least six-fold between 1979 and 2017. Glacier mass loss for 2015-2019 is the highest for any five-year period on record.
The four lowest records for winter also occurred during this period, with multi-year ice almost completely disappearing.
The amount of ice lost annually from the Antarctic ice sheet increased a least six-fold, said the report, from 40 Gt per year in 1979-1990 to 252 GT per year in the period 2009-2017.
The Greenland ice sheet has also seen an acceleration in ice loss since the turn of the millennium, it added.
“Sea level rise has accelerated and we are concerned that an abrupt decline in the Antarctic and Greenland ice sheets, which will exacerbate future rise. As we have seen this year with tragic effect in the Bahamas and Mozambique, sea-level rise and intense tropical storms led to humanitarian and economic catastrophes," said Taalas.
Rising acidity of ocean waters
Oceans absorb around 30% of the annual anthropogenic emissions of CO2, which helps alleviate some of the additional warming. However, the ecological impact for oceans is high since when mixed with seawater, the absorbed CO2 changes the level of acidity in the oceans, which is detrimental to marine ecosystems.
Extreme weather events
90% of extreme weather events such as storms, floodings, and heatwaves are related to weather. In the studied five-year period, heatwaves were the deadliest extreme weather event that affected all continents and resulted in various new temperature records.
Almost every scientific study of a significant heatwave has found links to climate change, said the report.
Extreme weather events can have very big economic and social impacts on a region, it said, highlighting the case of tropical cyclones, such as Hurricane Harvey, which caused the US more than $125 billion in losses.
Wildfires are also influenced by climate change, the report showed, as they lead to major releases of carbon dioxide to the atmosphere.
During the summer of 2019, unprecedented wildfires ravaged the Arctic region. Fifty megatons of carbon dioxide were emitted into the atmosphere in June as a result, which was more than was released by Arctic fires in the same month from 2010 to 2019 put together.
Widespread forest fires also ravaged parts of the Amazon tropical rainforest and forests in Southern Asia.
The report warned that because of the impacts of climate change, food insecurity and the risk of climate-related deaths were increasing.
Greenhouse gas emission levels at the point of no return
The report also noted that CO2 emissions from fossil fuel burning continue to grow by over 1% annually, reaching a new high.
In 2018, carbon dioxide emissions grew 2% and reached a record high of 37 billion tonnes of CO2 in 2018, with trends predicting they will be just as high in 2019.
Despite extraordinary growth in renewable fuels over the past decade, the global energy system is still dominated by fossil fuel sources. The annual increase in global energy use is greater than the increase in renewable energy, meaning fossil fuel use continues to grow. This growth needs to halt immediately.
The report also noted that global emissions are not estimated to peak by 2030, let alone by 2020.
What needs to be done?
The report highlights the urgent need to transform key human activities such as land exploitation or energy use to limit potentially irreversible impacts.
“It is highly important that we reduce greenhouse gas emissions, notably from energy production, industry and transport. This is critical if we are to mitigate climate change and meet the targets set out in the Paris Agreement,” said Taalas.
“To stop a global temperature increase of more than 2 degrees Celsius above pre-industrial levels, the level of ambition needs to be tripled. And to limit the increase to 1.5 degrees, it needs to be multiplied by five,” he said.