The year 2019 was overall the second-hottest ever recorded while - as far as months go - July 2019 was the warmest month ever recorded on Earth. According to NASA data, only 2016 exceeded the Earth's mean temperature (calculated for the years from 1980 to 2015 and used as a reference period for the chart) by more. As seen by the monthly temperatures of selected years since 1880, winter temperature is naturally below the multiyear mean of the reference period, which is a single figure showing the mean temperature over a long period of time irrespective of seasons.
Summer temperatures are naturally above the base period multiyear mean but have been diverging further and further from it. While monthly averages increased with every 20-year period, 2019 and 2016 were an even bigger jump up from the year 2000.
The global data for near-surface temperatures comes from onshore weather stations as well as from ship, buoys and satellite measurements of the oceans. According to scientific findings, the continuing global warming will lead to changes in the strength, frequency, spatial extent and duration of extreme weather events. 2019 heat also had a strong impact on polar ice conditions: The Arctic ice pack reached a historic low in July (19.8% below average), as did the Antarctic ice pack, which reached its smallest extent for July in 41 years of observations.