There is a one-in-10 chance that global average temperatures could "temporarily exceed" 1.5 ° C over pre-industrial levels for at least one year over the next five years, according to new Met Office analysis.
Such a breach would not mean that the world has "missed" the Paris Agreement's desire to limit man-made global warming to 1.5 C, researchers say Carbon Brief.
This is because the Paris target relates to stabilization of the global temperature to 1.5 C over longer periods of time up to 30 years. Thus, a potential overshoot should be seen as a "fluctuation" – and "does not mean" the Paris goal "can be discarded", a scientist adds.
The forecast expects that the average global surface temperature from 2019-23 should reach between 1.03 and 1.57C above pre-industrial levels. If realized, this would make the period from 2014-23 the hottest decade since records began more than 150 years ago.
The new analysis is a "decadal" forecast – a set of projections designed to capture climate fluctuations in the coming years.
To do this, researchers use global climate models that describe the effects of man-made climate change along with natural factors such as solar variation and the cooling impact of volcanic eruptions and natural aerosols.
The projections also consider how the conditions in the sea are likely to change in the coming years. This is influenced by natural phenomena such as El Niño, La Niña and the Atlantic Meridional Overrun Circulation (AMOC).
The results show that the global average temperature rise is likely to be between 1.03 C and 1.57 C over a five-year period from November 2018 to October 2023. This is shown in the chart below, where blue shade represents the range of expected temperature rise for that period compared to with temperatures in the "pre-industrial period" (1850-1990).
This chart also shows the actual temperature rise from 1960 to October 2018 in black, the results of previous Met Office decadal forecasts in red (hindcast) and results from the "Coupled Model Intercomparison Project" (CMIP5) in green.
Expected increase in global temperature from November 2018 to October 2023 (blue) compared to "pre-industrial" temperatures (1850-1900). The actual temperature rise from 1960 to October 2018 is shown in black, the results of previous Met Office decadal projections appear red (hindcast) and the results of the "Coupled Model Intercomparison Project" (CMIP5) appear in green. There is a gap between the black line and the blue shadow, because the observation data ends in October 2018, and the forecasts begin in November 2018. Shading shows the scope of self-confidence. Source: Met Office.
The animated "gif" below shows how Met Office's decadal projections have changed from 2013-19. (Met Met Office started producing decadal forecasts in December 2012 – but now releases forecasts starting at the end of the previous year in the following January or February.)
Met Office "decadal projections" from 2012-18. The projections (blue shadow) are relative to "industrial" temperatures (1850-1900). Actual temperature rise from 1960 is shown in black, the results of previous Met Office decadal projections appear red and the results of the "Coupled Model Intercomparison Project" (CMIP5) appear in green. In 2015, Met Office updated the method used in its forecasting system. Source: With Office / Carbon Letter.
If this year's forecast is realized, it would mean that the decade from 2014-23 will be the hottest ever recorded, the authors say.
(Analysis published today by the World Meteorological Organization (WMO) notes that the last four years have been the hottest on record – with 2016 the hottest year is recorded.)
The expected heat is a result of the world continuing to rapidly release greenhouse gases, the authors say:
"The forecast is for continued global warming driven largely by continued high levels of greenhouse gases. Other changes in the climate system, including a moderate La Niña in 2018 and long-term shifts in both Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), also contribute . "
(Carbon Brief has previously published articles explaining how PDO and AMOcan temporarily change the pace of global warming.)
1.5C still alive?
The analysis also finds that in the next five years, a 10% chance of global average temperature "temporarily exceeding" 1.5 C for one year. In a press release, Dr. Doug Smith, a Met Office research scientist, says:
"A temperature rise of 1 C or above will increase the risk of a temporary trip beyond the 1.5 C threshold above pre-industrial levels. Predictions now suggest about 10% chance of at least one year between 2019 and 2023 temporarily above 1.5 C."
This temporary violation would not mean that the world has missed the climatological goal of limiting global temperature rise to 1.5 C, Dr. Dr. Joeri Rogelj, a researcher at Imperial College London and a leading author of the Intergroup on Climate Change (IPCC) special report on 1.5 C. He tells Carbon Brief:
"International temperature targets are defined in" climatic "means – these are global temperatures that are typically average over 30 years. So over 1.5 C in any given year does not mean that the 1.5 C target has been broken and can be discarded. It is exactly what we expect when we approach a global warming limit of 1.5C. "
Another important thing to consider is that the Paris target is concerned about man-made global warming – while this forecast includes the influence of both human and natural factors, says Prof Piers Forster, director of the Priestley International Center for Climate at the University of Leeds and another leading author of the IPCC report on 1.5 C. He tells Carbon Brief:
The "1.5C goal is first and foremost a man-made warming goal – natural warming can heat or cool on many different schedules, but it is this human warming that matters in the long run and which society can act to reduce. "
In addition to looking at how the average global temperature can change, the forecast also prepares regional changes.
The charts below show expected warming from November 2018 to October 2023 worldwide over "pre-industrial" temperatures. Short "A" shows the "most likely prognosis outcome", the researchers say.
Meanwhile, the cards "B" and "C" show the projected range in forecast temperatures, they add. "We only expect 10% chance that temperatures in certain places are smaller than those in" B "and only 10% chance that temperatures will be higher than in C."
On all the cards, dark blue and green indicate temperature drop, while yellow, orange and red show the temperature rise.
Global distribution of expected heating in November 2018 to October 2023 worldwide compared to "pre-industrial" temperatures. Map "A" shows the most likely result, while "B" shows lower estimate and "C" shows upper estimate. On all the cards, dark blue and green indicate temperature drop, while yellow, orange and red show the temperature rise. Source: Met Office.
Map A indicates that heating is likely to be highest around the northern center widths and near the Arctic.
Earlier studies show that the temperature in the Arctic is rising at a rate that is more than twice as fast as the global average. A driving force for this is the reduction of Arctic sea ice. This is because as the ice melts, energy from the sun that would be reflected away would instead be absorbed by the ocean.
(Last week, the Carbon Brief announced in detail explaining how Arctic heating could affect extreme weather further away – also in the US and Western Europe.)
& # 39; Alarm Bells & # 39;
Although the new forecast does not show that we are breaking the Paris goal of limiting heating to 1.5 C, it may indicate that we are approaching, says Rogelj:
"Over 1.5 C of heating for a given year would not mean we missed the 1.5C target, but it does ring an alarm clock telling us that we are getting very close. Similarly, if a few colder years should be projected does not mean that heating has stopped and that we can emit much more greenhouse gases.
"The noise in the annual temperatures should not derail from the long-term trend."
The lack of the 1.5C target would mean violating a "safe" level of warming – but it may not necessarily rub ongoing climate change, he adds:
"It is important to note that governments support a 1.5 C temperature target because they consider it a level of warming that is acceptable or safe for their citizens and communities.
In fact, violating the level of global warming means that we have not been able to limit heating to the "safe" level, but that does not mean that climate change is suddenly to be rejected. The world does not end at 1.5 C, but at the same time, science also shows that serious effects can already be expected at 1.5 C heating. "
Source: CarbonBrief. Reproduced with permission.