Figure was reached at three decades ago; also, different regions warm at their own rates
Photo: iStock The 28th Conference of Parties (COP 28) to the United Nations Framework Convention on Climate Change scheduled from November 30-December 12, 2023 is bringing renewed focus on the Paris Agreement objective of capping the average global temperature increase at 2 degrees Celsius, or preferably 1.5°C above the preindustrial era.
The 1.5°C target, however, is fairly recent. "The original United Nations target of 2°C was chosen over 30 years ago to avoid the most dangerous effects of climate change," Manoj Joshi, Professor of Climate Dynamics at the School of Environmental Sciences, University of East Anglia, UK, told Down To Earth.
With greater understanding of climate change impacts, from forest fires to crop failures, in subsequent years, the 2015 Paris Agreement aimed to limit the temperature increase to 2°C, with 1.5°C as the preferred goal.
This objective was supported by a report that concluded that even a global warming of 1.5°C above the preindustrial average over an extended, decades-long period would pose high risks for "some regions and vulnerable ecosystems", according to MIT News.
Joshi explained that 1.5°C and 2°C are not specific thresholds beyond which physical impacts suddenly manifest in a given year or location.
Instead, he asserted that these goals reflect the fact that a warming world will experience more severe impacts, with significantly graver consequences under 2°C warming compared to 1.5°C.
Currently, the global average temperature has risen to 1.1°C relative to the 1800s and is projected to surpass the 1.5°C mark within the next decade. If business as usual continues, scientists express concern that the world could warm by 4.4°C by 2100.
The 1.5°C goal is far from perfect, as different regions warm at their own rates. For instance, the Arctic is warming at double, or even triple, the average global rate. The North Pole is also warming faster than the Antarctic.
This divergence implies that various regions will reach a 1.5°C increase at different times, as Joshi and his colleagues Tim Osborn and Phil Jones from the University of East Anglia explained in an interview.
“Using global temperature is simply a convenient metric to represent all of these changes in a single measure of the amount of climate change, in a similar way that Gross Domestic Product is an imperfect yet very useful measure of a country's economy,” Joshi explained.
Efforts to measure global average temperatures began in the 1800s. The first person to estimate a large-scale temperature average was Vladimir Köppen, a German meteorologist and climatologist, in the 1880s.
It was only in the mid-1980s that scientists gained access to ocean temperature data, thanks to the digitisation of ship logbook records.
This data was crucial because the ocean covers 70 per cent of the Earth’s surface and has absorbed 90 per cent of the warming in recent decades due to increasing greenhouse gases.
Six years later, in 1985, scientists from the University of East Anglia created a global picture of temperature averages by combining data from the land and ocean.
Today, with more instruments deployed to measure temperatures, scientists have gained deeper insights. In this decade alone, they have access to 8,000 weather station time series and about 260 million individual observations of sea surface and marine air temperatures from ships, experts from the University of East Anglia noted.
Nevertheless, uncertainties persist regarding the exact month or year when the 1.5°C goal will be surpassed. Joshi attributed this to uncertainties in past global temperature records, which stand at about 0.1°C, and natural climate variability, such as the El Niño Southern Oscillation, a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean.
To determine when warming will cross the 1.5°C mark, scientists will need to average the global temperature over multiple years, Joshi explained.
Some experts have raised doubts about the achievability of the 1.5°C goal, given the glacial pace of negotiations at COP. "I think it's extremely unlikely that warming will be limited to 1.5°C given the large gap between projected emissions of carbon dioxide and other anthropogenic greenhouse gases and the promised reductions in such gases by different countries," Joshi remarked.
The United Nations has also stated that the world is not on track to meet the Paris Agreement target of preventing global temperature from exceeding 1.5°C above pre-industrial levels.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
.png)
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.