July Climate Report: More Of The Same (Warm)

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Land and Sea temperature anomaly for July, 2014

Land and Sea temperature anomaly for July, 2014. Image courtesy of NCDC

NOAAs National Climate Data Center (NCDC) has released its report on global land and sea temperatures for July. The combined temperature was the fourth warmest ever for the month of July.

It was the 38th consecutive July and the 353rd consecutive month above the average of the 20th century.

The ocean tied its record for warmest July ever, while air temperatures lagged somewhat — tenth warmest.

The Overall Climate Trend

The jet stream pattern has shown a subtle change over several decades; the trend has accelerated in the last few years.

The circumpolar vortex — low pressure normally centered at the pole — has been disrupted by the powerful warming trend at high latitudes. The jet stream has been pushed south, and there is a marked increase in meridional flow (north to south and vice versa).

In addition, the jet stream waves seem to get stuck in place, bringing persistent warm or cold temperatures (and persistent drought or rain) to various regions for long periods of time.

The result of these changes is weather like that we experienced last winter: Very cold over the central and eastern United States and very warm in Europe. The pattern has continued into the summer.

Year-to-date global land and sea temperatures.  Graph courtesy of NCDC

Year-to-date global land and sea temperatures. Graph courtesy of NCDC

Temperature This July: Specifics Of The July Climate Report

Warm temperature anomalies persisted in July, as they have since last winter, over the western United States and the northeast Pacific Ocean. The wave in the jet stream connected with this warmth has a downstream component that brought continued cool weather to the central and eastern United States: Indiana and Arkansas recorded their warmest July in 120 years of data.

Europe also had unusual warmth in July, with records in several places:

  • It was the warmest July, in fact the warmest month ever, in Norway.
  • It was the second warmest July in Denmark.
  • Some western cities in Sweden, bordering Norway, broke their July temperature records by nearly two degrees.
  • July in the UK was the eighth warmest on record. Every month this year has been above normal.

How Much Precipitation: Specifics Of The July Climate Report

Precipitation can be highly variable from month to month — even hour to hour — so we can draw only tentative conclusions from the July precipitation. However, there were interesting anomalies.

The most notable precipitation departures from normal were in Europe, and these departures coincided with unusually warm temperatures. Since warm air holds more moisture than cold, this result is not unexpected.

France recorded its wettest July, with about twice the normal amount of precipitation, since countrywide record keeping began in 1959. Adjacent western Switzerland also had its wettest July. Germany recorded its tenth wettest July in 134 years of record keeping.

Australia’s rainfall was just 68% of normal. However, rainfall in Australia varies widely. Typically, Australia is very dry in El Niño years. Conditions are currently considered neutral, but El Niño is predicted to onset in the fall or winter. This could lead us to a chicken-and-egg discussion of what causes what.

Polar Ice Changes: Specifics Of The July Climate Report

The Arctic continues to lose ice at a rapid rate, while the Antarctic ice increases. There is no currently accepted theory as to why this is happening, but the net effect is loss of ice, which is in line with theories about the results of fossil fuel emissions on climate.

Land and sea temperature anomay for Jan-July, 2014. Image courtesy of NCDC

Land and sea temperature anomaly for Jan-July, 2014. Image courtesy of NCDC

Year-To-Date Global Climate And Prospects For The Full Year

The year-to-date temperature map looks much like that of July. The cold pocket over central North America is quite pronounced, as are the warm spots: Europe and the Gulf of Alaska.

The year has settled in to third place for all-time warmest year, but the two front-runners — 1998 and 2010 — both cooled relative to normal towards the end of the year. 2014 may end up the warmest year ever, especially if the anticipated El Niño develops.

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