New Delhi: Even as climate change sceptics rubbish rising global temperature, a latest report by US-based Nasa (National Aeronautics and Space Administration) has said that Earth’s global surface temperature in 2017 ranked as the second warmest since 1880 when global estimates became feasible.
It also stressed that if the effects of the “recent El Niño and La Niña patterns were statistically removed from the record, 2017 would have been the warmest year on record."
But this is not where the worrying trend ends as the analysis also emphasises that with this continues a decades-long warming trend—17 of the 18 warmest years have now occurred since 2001.
“Continuing the planet’s long-term warming trend, globally averaged temperatures in 2017 were 1.62 degrees Fahrenheit (0.90 degrees Celsius) warmer than the 1951 to 1980 mean," said the analysis released on Thursday by Nasa’s Goddard Institute for Space Studies (GISS) in New York, while adding that it is second only to global temperatures in 2016.
As per the analysis, Earth’s average surface temperature has risen about 2 degrees Fahrenheit (a little more than 1 degree Celsius) during the last century or so, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere.
“Last year was the third consecutive year in which global temperatures were more than 1.8 degrees Fahrenheit (1 degree Celsius) above late nineteenth-century levels," it added.
The analysis is significant for policymakers because as per Nasa rising global temperatures are already creating impacts around the world.
“Fire seasons are longer and more intense, and melting ice contributes to rising sea levels" the analysis added.
For a country like India which has a vast coastline of about 7500 km inhabited by millions, the rising sea level means trouble.
India’s major cities like Mumbai, which is called country’s financial capital, and Kolkata are among the top 10 megacities across the world that face a serious threat due to rising sea levels. It had said that India has 55 million inhabitants endangered by 4°C warming by end of year 2100, while 20 million are at risk from 2°C warming. As any as 11 million people are at risk in Mumbai alone if the global temperature rises by 4°C and 5.8 million in case of 2°C .
A warming trend could also have a significant impact on the monsoon. According to a study done at the Indian Institute of Tropical Meteorology, Pune, using longitudinal rainfall data from 1901-2012, rainfall has been decreasing over central South Asia — from south of Pakistan through central India to Bangladesh. The decrease is highly significant over central India where agriculture is still mostly rain-fed, with reduction of up to 10-20% in the mean rainfall.
In December 2015, 195 nations adopted the Paris Agreement under the United Nations Framework Convention on Climate Change (UNFCCC) that aims to limit rise in global temperature well below 2 degrees Celsius over pre-industrial times and make efforts to limit it to 1.5 degrees Celsius above pre-industrial levels by the end of 2100.
But interestingly, it was US President Donald Trump, who in June 2017 announced withdrawal from the global climate deal while crying foul that the Paris Climate Agreement favours world’s leading polluters like India and China, while being unfair to the United States.
Meanwhile, in a separate independent analysis, scientists at the US-based National Oceanic and Atmospheric Administration (NOAA) concluded that 2017 was the third-warmest year in their record.
It warned that warming trends are strongest in the Arctic regions, where 2017 saw the continued loss of sea ice.
An official Nasa statement said that the “minor difference in rankings is due to the different methods used by the two agencies to analyze global temperatures, although over the long-term the agencies’ records remain in strong agreement."
“Both analyses show that the five warmest years on record all have taken place since 2010," it added.
“Despite colder than average temperatures in any one part of the world, temperatures over the planet as a whole continue the rapid warming trend we’ve seen over the last 40 years," said Nasa’s GISS director Gavin Schmidt.
Explaining further, the NASA report said that phenomena such as “El Niño or La Niña, which warm or cool the upper tropical Pacific Ocean and cause corresponding variations in global wind and weather patterns, contribute to short-term variations in global average temperature."
“A warming El Niño event was in effect for most of 2015 and the first third of 2016. Even without an El Niño event—and with a La Niña starting in the later months of 2017—last year’s temperatures ranked between 2015 and 2016," it added.
But rise in temperature is not uniform across various regions of world as “weather dynamics often affect regional temperatures".
For instance, as per NOAA, in the US, 2017 was the third warmest year on record.
Nasa’s study was based on surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations.
“These raw measurements are analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heating effects that could skew the conclusions.These calculations produce the global average temperature deviations from the baseline period of 1951 to 1980," Nasa explained.
NOAA analysis used much of the same raw temperature data, but with a different baseline period, and different methods to analyze Earth’s polar regions and global temperatures.