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he NOAA Coral Reef Watch (CRW) Coral Bleaching Thermal Stress Outlook indicates that there is a high potential for coral bleaching in the Caribbean in 2010. The 2009-2010 El Niño ended in May 2010. However, the Caribbean typically experiences elevated temperature during the second year of an El Niño event. Since the beginning of 2010, sea surface temperatures (SSTs) in most of the Caribbean region and tropical Atlantic Ocean have been observed more than 1ºC above the normal (see the SST anomaly figure below), based on Coral Reef Watch's climatology. This pattern is similar to, but has persisted much longer than, what occurred during the same time period in 2005.

The NOAA Coral Reef Watch (CRW) Coral Bleaching Thermal Stress Outlook indicates that there is a high potential for coral bleaching in the Caribbean in 2010. The 2009-2010 El Niño ended in May 2010. However, the Caribbean usually experiences elevated temperature during the year following an El Niño event. Since the beginning of 2010, sea surface temperatures (SSTs) in most of the Caribbean region and tropical Atlantic Ocean have been observed more than 1ºC above the normal (see the SST anomaly figure above), based on Coral Reef Watch's climatology. This pattern is similar to, but has persisted much longer than, what occurred during the same time period in 2005. In 2005, a record breaking mass coral bleaching event in the Caribbean along with the most active hurricane season on record in the Atlantic Ocean followed such a pre-bleaching season SST anomaly pattern. The high SST anomaly in the Gulf of Mexico and Florida Keys began in mid-May after a dramatic increase in SST in early May (near 2ºC increase over several days at some locations) after an extreme cold outbreak earlier this year in the eastern Gulf of Mexico and Florida area. This preheating increases the likelihood that temperatures will exceed bleaching thresholds during the coming season. The pattern and intensity of early-season SST anomalies is similar to what was seen in 2005. The high potential for thermal stress above levels required to cause bleaching as seen in the CRW bleaching outlook system indicates a high potential for significant bleaching in the Caribbean region for the 2010 bleaching season. In 2005, the active hurricane season greatly reduced the coral bleaching thermal stress in the Florida Keys and Gulf of Mexico. However, the lack of tropical cyclones around the Lesser Antilles did not allow storms to relieve much the thermal stress in the epicenter of the 2005 mass bleaching event.

Low level bleaching thermal stress has already been present in the Caribbean region. The stress started to appear at the beginning of May at the eastern end of the Caribbean. It now covers most of the southern Caribbean region. In the Caribbean, bleaching-level thermal stress usually does not appear across such a wide area this early in the year. The year of 2005 was an exception and showed the similar thermal stress pattern. Given that the record breaking mass coral bleaching event occurred in 2005, the development of this year's thermal stress in the Caribbean needs to be monitored closely.

June SSTs in the tropical Atlantic set a new recordSea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest June on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 1.33°C above average during June, beating the previous record of 1.26°C set in June 2005. June 2010 is the fifth straight record warm month in the tropical Atlantic, and the third warmest anomaly measured for any month in history. The only warmer anomalies were 1.51°C and 1.46°C, set in May 2010 and April 2010, respectively.

In a Congressional briefing on 30 June 2010, hurricane expert Greg Holland of the National Center for Atmospheric Research (NCAR) said the potential for a disastrous 2010 hurricane season reflects not just natural variability but also climate change.  He explained that record high sea surface temperatures in the tropical Atlantic were one of the principal factors behind the dire forecast, and that rising atmospheric concentrations of greenhouse gases may account for roughly half of the anomalous warmth.  He warned that "we’re looking at potentially a doubling of major hurricanes in the next 20 to 30 years" as a result of global warming.  Holland, Director of NCAR's Earth System Laboratory, made his remarks as a member of a panel on Hurricanes and Oil Will Mix: Managing Risk Now. 

A month before the panel's briefing, the National Oceanic and Atmospheric Administration (NOAA) issued on 27 May its 2010 Atlantic Hurricane Season Outlook. NOAA said there was a 70% chance that the Atlantic hurricane season would see 14-23 named storms, 8-14 hurricanes, and 3-7 major hurricanes.

Among the factors underlying its outlook, NOAA cited warm Atlantic Ocean surface waters, which in May were for the fourth month in a row at record high temperatures for the month:  "Sea surface temperatures [SSTs] are expected to remain above average where storms often develop and move across the Atlantic. Record warm temperatures – up to four degrees Fahrenheit above average – are now present in this region."