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Scientists say 2017 was second hottest year on record without El Nino

Last year was the second  hottest year on record – after 2016 and on a par with 2015, according to data. The bad news though is that 2015 and 2016 temperature recordings were effected by El Nino.

The finding by the National Aeronautics and Space Administration (NASA) follows three years in a row in which global temperature hit a new record. Last year’s average temperature was eclipsed only by 2016’s.

The heat average follows a decades-long trend of rising global temperatures, which researchers say is nearly certain to be a sign of climate change, attributable primarily to greenhouse gas emissions caused by human activity.

By both analyses, 17 of the 18 warmest years since modern record keeping began in 1880 have occurred since 2001. Overall, fueled by emissions of carbon dioxide and other greenhouse gases, temperatures have increased more than 1 degree Celsius (1.8 degrees Fahrenheit) since the late 19th century.

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 in NASA’s records.

In an analysis where 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.

Weather dynamics often affect regional temperatures, so not every region on Earth experienced similar amounts of warming. NOAA found the 2017 annual mean temperature for the contiguous 48 United States was the third warmest on record.

Warming trends are strongest in the Arctic regions, where 2017 saw the continued loss of sea ice.

NASA’s temperature analyses incorporate 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.

NOAA scientists 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.

In order to avoid the worst consequences of climate change, scientists say global temperatures must not increase more than 2 degrees Celsius.

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