In more news that's both concerning and unsurprising, several climate reports released today have concluded that 2018 was among the hottest years on record. In independent analyses, NASA, the National Oceanic and Atmospheric Administration (NOAA) and the World Meteorological Organization (WMO) have all found that the past year continued a long-term upward trend.

In all three reports, 2018 was found to be the fourth warmest year on record, with 2016 still topping the list thanks to a strong El Nino effect, followed closely by 2017 and then 2015. Collectively the past five years are the hottest in the modern record, which began in 1880, while the 20 hottest have all been within the last 22 years.

Those figures are calculated by analyzing data gathered by 6,300 weather stations around the world, along with temperature readings from research stations in Antarctica and surface temperatures collected by ships and buoys. The raw data is then analyzed in different ways by the different organizations.

NASA says the average global temperature has risen by about 1° C (2° F) since records began in 1880. In 2018, that average was 0.83° C (1.5° F) warmer than the 1951 to 1980 mean. That 30-year period, according to NASA's data, was when temperature averages generally held flat, fluctuating fairly consistently around a central point. Since then, there's been a clear and sharp upward trend – in fact, NOAA says that every year since 1977 has had an above-average temperature.

NOAA processes the data differently, taking an average of each year in the 20th century. According to those calculations, the average global temperature in 2018 was 0.79° C (1.42° F) warmer than the 20th century average.

The WMO report, meanwhile, uses a different period again – a long-term average of the 30 years between 1981 and 2010. The global average temperature in 2018 was about 0.38° C (0.68° F) above that baseline, which is estimated to be 14.3° C (57.7° F).

While it may seem odd and potentially contradictory that different reports are returning different figures, it's important to understand that in the big picture, they're all largely in agreement. As the graph above shows, while there may be slight variations in any given year, the overall peaks and valleys line up closely, as does the clear upwards trend in the last few decades.

The results of the NASA study are detailed in the video below.

Sources: NASA, NOAA, WMO

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