Following are highlights from the global portion of the September, 2017 NOAA State of the Climate Report reviewing the January through September time period. -- Bryce
The first nine months of the year have each ranked among the top four warmest months on record, giving way to the second highest January-September period in the 138-year record at 0.87 deg C (1.57 deg F) above the 20th century average of 14.1 deg C (57.5 deg F), trailing behind the record year of 2016 by 0.13 deg C (0.23 deg F), but ahead of 2015 by 0.01 deg C (0.02 deg F). Nine of the 10 warmest January-September global land and ocean temperatures occurred during the 21st century (since 2005), with only one year from the 20th century (1998) among the top 10. Based on three simple scenarios, 2017 will likely end up among the top three warmest years on record.
Much of the world's land and ocean surfaces had warmer to much-warmer-than-average conditions during the first nine months of the year, with limited areas experiencing near to cooler-than-average conditions. Record warmth was observed across parts of eastern Asia, the western and central Pacific Ocean, western Indian Ocean, western Europe and surrounding oceans, and scattered across southern North America, southern South America, southern Africa, and Australia. No land or ocean areas experienced record cold September temperatures.
According to the National Center for Environmental Information (NCEI) Regional Analysis, all six continents had a top seven warm January-September period, with South America having its second highest September temperature on record, behind 2015. The global land surface temperature was 1.37 deg C (2.47 deg F) above the 20th century average of 9.3 deg C (48.7 deg F) and the second highest value for the year-to-date, behind 2016 by 0.21 deg C (0.38 deg F). The global ocean surface temperature was the third highest such period at 0.68 deg C (1.22 deg F) above the 20th century average of 16.1 deg C (61.1 deg F), behind 2016 (0.79 C or 1.42 F above the 20th century average) and 2015 (0.70 C or 1.26 F above the 20th century average).
September precipitation was generally drier than normal across parts of the eastern half of the contiguous U.S., northeastern Brazil as well as parts of southern South America, western and southeastern Europe, Australia, and scattered across western and southern Africa, and Asia. Wetter-than-normal conditions were notable across the western half of the contiguous U.S., northeastern Argentina, eastern Europe, Mongolia, and parts of south-central Russia.
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Select national information is highlighted below. (Please note that different countries report anomalies with respect to different base periods. The information provided here is based directly upon these data):
Portugal experienced very hot temperatures that exacerbated the drought conditions across the nation. The much-drier-than-average conditions plagued Portugal during September 2017, resulting in the driest September in 87 years. As of September 30, 81.0 percent of the nation was in severe drought, while 7.4 percent was in extreme drought, according to the Portuguese Institute for Sea and Atmosphere.
Denmark's precipitation total for September 2017 was 109 mm (4.3 inches) -- the wettest September since 2001 (137 mm or 5.4 inches) and the wettest month for any month since December 2015.
Much of New Zealand had above to much-above-average conditions during September 2017, with several locations setting monthly or daily rainfall records and near-records. Hanmer Forest reported a total of 126 mm (5.0 inches) in a 24-hour period on September 18—the highest one-day September rainfall since records began in 1905. South West Cape had its wettest September (163 percent of normal) since its records began in 1991.
Below-average precipitation was observed across parts of northern and the southern half of Argentina during September 2017. However, parts of northeastern Argentina had above-average conditions, with several locations (Gualeguaychu, Las Flores, and Azul) having their wettest September in the last decades.
Much of Fiji continued to experience drier-than-average conditions, with over 70 percent of the stations experiencing below- to much-below-average conditions. According to Fiji's Meteorological Service, only six of 23 rainfall monitoring stations had near to above-average conditions.
Australia as a whole had below-average precipitation at 66 percent of September normal precipitation total and the 35th driest September in the 118-year record. Regionally, Queensland had its lowest September since 2003 and the tenth lowest in the record, receiving only 12 percent of its normal precipitation for the month. New South Wales had 14 percent of the month's total precipitation, resulting in the driest September on record.
SNOW AND ICE
According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere (Arctic) sea ice extent -- which is measured from passive microwave instruments onboard NOAA satellites -- averaged for September 2017 was 4.87 million square km (1.88 million square miles), 1.67 million square km (650,000 square miles), or 25.54 percent, below the 1981-2010 average. This was the seventh smallest September Arctic sea ice extent on record and 1.24 million square kilometers (479,000 square miles) above the record low September set in 2012. September was marked by sea ice retreat early in the month and sea ice expansion after the 13th when the annual minimum extent occurred. Sea ice expanded rapidly during the second half of September, especially along the Siberian side of the Arctic. Regionally, much-below-average sea ice was observed for the Beaufort and Chukchi Seas. September Arctic sea ice extent is decreasing at an average rate of 12.8 percent per decade.
The September Southern Hemisphere (Antarctic) sea ice extent was 18.03 million square km (6.96 million square miles), which was 850,000 square km (330,000 square miles), or 4.51 percent, below the 1981-2010 average. This was the second smallest September Southern Hemisphere sea ice extent on record and only slightly larger than the September extent in 1986. Southern Hemisphere September sea ice extent is increasing at an average rate of 0.69 percent per decade, with substantial inter-annual variability. It appeared that the Antarctic sea ice extent might have reached its annual maximum extent in mid-September, but a late-season surge in ice expansion caused the maximum to occur in mid-October.
The full report is available here. https://goo.gl/…
Bryce Anderson can be reached at firstname.lastname@example.org
Follow him on Twitter @BAndersonDTN
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