Temperatures in New York are increasing, and after 2047 they won’t return to the historical average of the past one and half centuries, according to a study today in the journal Nature.
“Climate departure,” when the average temperature for each year is expected to exceed historical averages from 1860 through 2005, will occur in Jakarta and Lagos in 2029, Beijing in 2046 and London in 2056, according to the study. New York will match the global departure 34 years from now and tropical areas will get there sooner.
The research highlights the urgency of cutting greenhouse-gas emissions because the warming climate may drive some species to extinction, threaten food supplies and spread disease, according to the study. By 2050, 5 billion people may face extreme climates, and migration and heightened competition for natural resources may trigger violence and instability.
“The results shocked us: regardless of the scenario, changes will be coming soon,” Camilo Mora, a geographer at the University of Hawaii at Manoa and lead author of the study, said in a statement. “Within my generation, whatever climate we were used to will be a thing of the past.”
The global point of climate departure will be 2047, with tropical areas reaching it earlier.
“The tropics will experience unprecedented warming 15 years earlier than the rest of the world,” Mora told reporters on a conference call. “We were very conservative when we started this index and were pretty surprised how early some of these change would take place.”
The forecast assumes that carbon emissions will continue at a “business-as-usual” pace, according to the study. Under a separate scenario that assumes greenhouse gases are stabilized, the global climate departure is delayed more than two decades, until 2069.
New York, under the more “optimistic” scenario, would experience unprecedented warming by 2072. The city was pummeled by Hurricane Sandy a year ago, leading to insured losses of about $25 billion in the U.S. according to Munich Re estimates. President Barack Obama cited the storm in his State of the Union address this year as a sign of the urgent need to address climate change.
Changes will occur in the tropics sooner because they have a less variable climate, so even a small change in average temperature can take an area outside historical norms, according to the study. That may harm biodiversity in lower latitudes because tropical plants and animals are suited only to smaller variations in the climate, the researchers wrote.
“Conservation practitioners take heed: the climate-change race is not only on, it is fixed, with the extinction finish line looming closest for the tropics,” Eric Post, a professor of biology at Pennsylvania State University, wrote in an accompanying article in Nature.
The study used as a baseline the average annual temperatures in cities around the world for each year from 1860 through 2005. While some years in the next few decades are predicted to exceed the highest of those averages, later years will return to levels within the historical average. Climate departure is the point when temperatures go outside that band and all subsequent years will exceed the range.
That will occur in Mexico City in 2031, Mumbai in 2034, Baghdad, Cairo and Nairobi in 2036, Tokyo in 2041, Rome in 2044, Bangkok in 2046, and Rio de Janeiro in 2050. The Indonesian city of Manokwari is expected to get there first, in 2020.
The results highlight the challenge faced by United Nations envoys who are trying to negotiate by 2015 a binding treaty to combat climate change that would take effect from 2020.
World leaders have agreed to contain temperature rises since industrialization to 2 degrees Celsius (3.6 degrees Fahrenheit), and the UN last month said the planet has already warmed by an average 0.85 degree since 1880. The World Bank last year said the planet is on track to warm 4 degrees by 2100.
Fourteen researchers at the University of Hawaii and Japan’s University of the Ryukyus contributed to the study, which used projections from 39 computer models that analyze multiple climate variables, including air temperature, precipitation, evaporation and the acidity of the oceans.
While the study focused on air temperatures, the authors also said the global average pH of the ocean -- a measure of acidity -- departed from its norm in 2008, because of narrow historical variability of the measure.
“We are pushing the ecosystems of the world out of the environment in which they evolved into wholly new conditions that they may not be able to cope with,” Ken Caldeira, a climate scientist at the Carnegie Institution for Science, said in the statement. “Some ecosystems may be able to adapt, but for others, such as coral reefs, complete loss of not only individual species but their entire integrity is likely.”