The Earth has reached a grim milestone in its fight against climate change. According to the latest report from the World Meteorological Organization (WMO), there is a 66% chance that the global annual mean temperature will exceed 1.5°C above pre-industrial levels in the next five years. This is the first time that the world is likely to cross this critical threshold, which was set as a goal by the 2015 Paris Agreement to avoid the worst impacts of global warming.
The WMO report, which is based on data from 10 different climate models, shows that the probability of breaching 1.5°C has increased significantly since last year, when it was estimated at 50%. The report also warns that the world is on track to reach 1.5°C of warming by the early 2030s, unless drastic and immediate actions are taken to reduce greenhouse gas emissions.
The 1.5°C limit is not a direct measure of the world’s temperature, but an indicator of how much the planet has warmed or cooled compared to the long-term global average. Scientists use the period between 1850 and 1900 as a reference point, before the industrial revolution and the widespread use of fossil fuels. Since then, the Earth’s temperature has risen by about 1.1°C, mainly due to the burning of coal, oil and gas.
Why 1.5°C Matters
The 1.5°C limit was chosen as a target by the Paris Agreement because it represents a level of warming that would still allow the world to cope with some of the effects of climate change, such as more frequent and intense heat waves, droughts, floods, storms and wildfires. However, going beyond 1.5°C would pose severe risks to human health, food security, water availability, biodiversity and ecosystems.
According to a landmark report by the Intergovernmental Panel on Climate Change (IPCC) in 2018, limiting warming to 1.5°C would require global emissions to be halved by 2030 and reach net zero by 2050. This would entail a rapid and unprecedented transformation of the world’s energy, transport, industry and land use sectors. The report also warned that every fraction of a degree of warming matters, as it would increase the likelihood and severity of climate impacts.
However, the current pledges and actions by countries to reduce their emissions are far from sufficient to meet the 1.5°C goal. According to the United Nations Environment Programme (UNEP), the world is heading for a temperature rise of 3°C or more by the end of the century, unless there is a dramatic increase in ambition and action. The UNEP also estimates that the world has already used up about 80% of its carbon budget, which is the amount of CO2 that can be emitted without exceeding 1.5°C of warming.
A Temporary or Permanent Breach?
The WMO report cautions that crossing the 1.5°C threshold in any one year does not mean that the Paris limit has been broken for good. The global temperature fluctuates from year to year due to natural variability, such as the El Niño and La Niña phenomena, which affect the surface temperature of the Pacific Ocean and influence weather patterns around the world. For example, El Niño tends to increase the global temperature, while La Niña tends to decrease it.
Therefore, a single year of warming above 1.5°C could be followed by a year of cooling below it, depending on the natural variability. However, the report also stresses that the world is edging ever closer to a situation where 1.5°C could be exceeded for an extended period, or even permanently, unless emissions are drastically reduced. The report also notes that the longer-term trend of warming is more important than the values for individual years, as it reflects the cumulative effect of human activities on the climate system.
The WMO report is the latest in a series of alarming scientific findings that highlight the urgency and magnitude of the climate crisis. Earlier this year, the WMO reported that the concentration of CO2 in the atmosphere reached a record high of 417 parts per million in May 2020, despite a temporary drop in emissions due to the Covid-19 pandemic. The last time CO2 levels exceeded 400 parts per million was around four million years ago, during the Pliocene era, when the global temperature was 2-4°C warmer and the sea level was 10-25 meters higher than today.
The WMO report also comes ahead of the 26th Conference of the Parties (COP26) to the United Nations Framework Convention on Climate Change (UNFCCC), which will be held in Glasgow, Scotland, in November 2021. The COP26 is expected to be a crucial moment for the world to demonstrate its commitment and action to achieve the goals of the Paris Agreement, and to avoid crossing the 1.5°C threshold for good.