The World Meteorological Organization (WMO) said there was a 40% chance of the watershed global warming mark being met during the time frame, and these odds are increasing with time.
The 1.5°C marks were established as the desirable target for all the countries of the world who signed up to the Paris Agreement to limit temperature rises, in order to prevent permanent changes that threaten the wellbeing of all life on earth. The agreement calls for limiting rises to 2°C or below.
There is a 90% likelihood of at least one year between 2021-2025 becoming the warmest on record, which would dislodge 2016 from the top ranking, according to the Global Annual to Decadal Climate Update produced by the United Kingdom's Met Office, the WMO lead centre for such predictions.
More rain, cyclones
Up to the end of 2025, high-latitude regions and the Sahel are likely to be wetter, the report suggests, and there is an increased chance of more tropical cyclones in the Atlantic compared to the average, taken from the start of the 1980s.
The annual update harnesses the expertise of internationally acclaimed climate scientists and the best prediction systems from leading climate centres around the world to produce actionable information.
"These are more than just statistics", said WMO Secretary-General Petteri Taalas. "Increasing temperatures mean more melting ice, higher sea levels, more heatwaves and other extreme weather, and greater impacts on food security, health, the environment and sustainable development," he said.
'Yet another wake-up call'
"This study shows – with a high level of scientific skill – that we are getting measurably and inexorably closer to the lower target of the Paris Agreement on Climate Change.
"It is yet another wake-up call that the world needs to fast-track commitments to slash greenhouse gas emissions and achieve carbon neutrality", said Professor Taalas. "Technological advances now make it possible to track greenhouse gas emissions back to their sources as a means of precisely targeting reduction efforts", he noted.
Sunrise in the Ebro Delta in Spain's Catalonia region., by WMO/Agusti Descarrega Sola
He said the report also underlines the need for climate adaptation. "Only half of 193 WMO Members have state of the art early warning services. Countries should continue to develop the services that will be needed to support adaptation in climate-sensitive sectors – such as health, water, agriculture and renewable energy – and promote early warning systems that reduce the adverse impacts of extreme events" he said.
"Besides limitations in early warning services we are having severe gaps in weather observations especially in Africa and island states. This has a major negative impact on the accuracy if the early warnings in those areas and globally. We need to invest in the basic networks as well." he concluded.
In 2020 – one of the three warmest years on record – the global average temperature was 1.2 °C above the pre-industrial baseline, according to the WMO's report on the State of the Global Climate 2020, released in April. It highlighted the acceleration in climate change indicators like rising sea levels, melting sea ice, and extreme weather, as well as worsening impacts on socio-economic development.
And Thursday's update confirms that trend. In the coming five years, the annual mean global temperature is likely to be at least 1°C warmer – within the range 0.9°C – 1.8°C – than preindustrial levels.
The chance of temporarily reaching 1.5°C has roughly doubled compared to last year's predictions, said WMO. This is mainly due to using an improved temperature dataset to estimate the baseline rather than sudden changes in climate indicators.
This current year and the crucial climate change negotiations, COP26, in November, has been widely described as a "make-or-break" chance to prevent climate change spiralling ever more out of control, noted WMO. Tackling climate change is high on the agenda of the G7 leader's summit, due to be hosted by the UK from 11-13 June.