Climate Change Blogs

Record Ocean Temperatures Threaten Hawaii's Coral Reefs

Published: July 24, 2015
Record warm sea surface temperatures in Hawaii's waters threaten to bring a second consecutive year of record coral bleaching to their precious coral reefs this summer. According to NOAA, ocean temperatures in the waters near and to the south of the Hawaiian Islands were 1 - 2°C (1.8 - 3.6°F) above average in June, which was the warmest these waters have been since record keeping began over a century ago. With the waters surrounding Hawaii expected to warm to their highest values of the summer by September, and likely remain 1 - 2°C above average, NOAA's Coral Reef Watch has placed the islands under a Coral Bleach Watch, and their experimental coral bleaching forecast gives a 50 - 90% chance that Hawaii will experience "Level 2" thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality. The record warm ocean temperatures are due to a strong El Niño event that is pushing large amounts of record-warm water into the Central Pacific, in combination with the steady rise in ocean temperatures due to global warming. Mass coral die-offs commonly occur during strong El Niño events; the United Nations Environmental Program found that 16% of the worlds coral reefs were effectively lost during a nine-month coral bleaching episode associated with the 1997 - 1998 record-strength El Niño event. With this year's El Niño event likely to be almost as strong as the 1997 - 1998 one, coral reefs are going to take a beating again.

Figure 1. NOAA's experimental coral bleaching forecast gives a 50 - 90% chance that Hawaii will experience Satellite Bleaching Alert Level 2 thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality. El Niño conditions have produced an extremely warm band of water from the central equatorial Pacific to the South American coast, and Level 2 thermal stress has already been reached in the Gilbert, Phoenix, and Northern Line Islands in Kiribati, as well as in Micronesia, the Howland and Baker Islands, and to the east in the Galápagos.

Figure 2. Unusually warm waters are also in place along the northern coast of Cuba and in the Bahamas, and NOAA's experimental coral bleaching forecast gives about a 70% chance coral reefs in these waters will experience Satellite Bleaching Alert Level 2 thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality.

Second consecutive year of severe coral bleaching in Hawaii
Hawaii's reefs are already reeling from their worst coral bleaching event in recorded history in 2014, when record warm ocean temperatures caused 50 - 70% of the corals sampled in Northeast Oahu's Kāneʻohe Bay to bleach. When the sea surface temperature is 1°C warmer than the highest monthly mean temperature corals usually experience, coral polyps will expel the symbiotic algae that live in their tissues, exposing the white skeleton underneath, resulting in a white "bleached" appearance. Death can result if the stress is high and long-lived. In Hawaii's waters, corals cannot tolerate water temperatures above 83°F (28.3°C) for multi-week periods without suffering bleaching. Corals typically recover from mild bleaching, gradually recovering their color by repopulating their algae. However, if the bleaching is severe or prolonged, individual polyps or whole colonies will die. With Hawaii likely to undergo a second consecutive year of record warm waters and coral bleaching in 2015, widespread mortality in many of Hawaii's coral reefs is possible, particularly around the Big Island.

Figure 3. During June 2015, the ocean areas near and to the south of Hawaii were at their warmest levels since record keeping began in 1880. Image credit: National Centers for Environmental Information (NCEI) .

Could a hurricane help?
When hurricanes and tropical storms churn the waters, they upwell large amounts of cooler waters from the depths that can cool the surface waters, potentially reducing the thermal stress on coral reefs. The heavy rains from the storm can also potentially cause cooling. This occurred in the Virgin Islands in 2010, when Hurricane Earl and Hurricane Otto helped relieve a potentially dangerous coral bleaching episode (Figure 4.) So, should Hawaii hope for a hurricane this September to help save its coral reefs? Well, be careful what you wish for. Hurricanes cause damage to reefs. Following Tropical Storm Iselle, which hit the Big Island of Hawaii on August 7, 2014, with 60 mph winds, researchers at the University of Hawaii, Hilo documented that one coral reef on the Big Island (the Wai`ōpae tide pools) suffered physical damage from pounding waves that broke up to 18% of the coral colonies of one species of coral with long slender branches--cauliflower coral. Other corals suffered lesser damage, 0 - 10% breakage. In addition, these corals were subjected to sewage contamination due to damage of cesspools and septic tanks.

Figure 4. Mean daily temperatures (on left Y-axis) with standard error collected at reef-depth (26'-58') monitoring sites on St. John US Virgin Islands, and total daily rainfall (on right Y-axis) from August through October 2010 from Newfound, Haulover, Tektite, Yawzi and Mennebeck Reefs in the Virgin Islands. Image credit: Rafe Boulon, Resource Management Chief, Virgin Islands National Park.

Long term outlook for world's coral reefs: bleak
The large amount of carbon dioxide humans have put into the air in recent decades has done more than just raise Earth's global temperature--it has also increased the acidity of the oceans, since carbon dioxide dissolves in sea water to form carbonic acid. The oceans are acidifying faster than at any time in the past 300 million years. Corals have trouble growing in acidic sea water, and the combined effects of increasing ocean temperatures, increasing acidity, pollution, and overfishing have reduced coral reefs globally by 19 percent between 1950 - 2008. Another 35 percent could disappear in the next 40 years, even without the impact of climate change, according to a report released in October 2010 by the World Meteorological Organization and the Convention on Biological Diversity.

Coral expert J.E.N. Veron, former chief scientist of the Australian Institute of Marine Science, had this to say in an excellent interview he did with Yale Environment 360 in 2010: "the science is clear: Unless we change the way we live, the Earth's coral reefs will be utterly destroyed within our children's lifetimes...Reefs are the ocean's canaries and we must hear their call. This call is not just for themselves, for the other great ecosystems of the ocean stand behind reefs like a row of dominoes. If coral reefs fail, the rest will follow in rapid succession, and the Sixth Mass Extinction will be upon us--and will be of our making."

Figure 5. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

Jeff Masters
Categories:Climate Change

Fewer but Stronger Global Tropical Cyclones Due to Ocean Warming

Published: July 23, 2015
Global ocean temperatures hit their warmest levels in recorded history last month. Since hurricanes are heat engines which extract heat energy from the oceans and convert it to the kinetic energy of the storms' winds, we should be concerned about the potential for hurricanes to be stronger as a result of global warming. Indeed, the observed 0.3°C (0.5°F) warming of Earth's oceans over the past 30 years has made more energy available to hurricanes, says a new study published in May in Nature Climate Change by Florida State hurricane scientist James Elsner and the deputy director of the National Typhoon Center in South Korea, Namyoung Kang. The researchers found that this extra heat energy has led to a change in both the frequency and intensity of global tropical storms and hurricanes. Using a new mathematical framework to categorize all global tropical cyclones with wind speeds of at least 39 mph over the past 30 years, the authors showed that the observed warming of Earth's oceans during that time period has led to an average increase in wind speed of about 3 mph (1.3 m/s) for each storm--but there were 6.1 fewer named storms globally each year because of the warmer oceans. A typical year has about 85 named storms globally, so this represents about a 7% decrease in the number of storms.

Figure 1. One of the most spectacular images ever captured of a tropical cyclone from space: Category 5 Super Typhoon Maysak as seen from the International Space Station at approximately 6 pm EDT Tuesday March 31, 2015 (just after dawn local time.) At the time, Mayask had top winds of 160 mph as estimated by the Joint Typhoon Warning Center, and a central pressure of 905 mb, as estimated by the Japan Meteorological Agency. Image has been brightened and flipped 180 degrees. Image credit: Terry W. Virts.

Why fewer storms, but the strongest ones getting stronger?
More moisture is evaporated from a warmer ocean surface, resulting in water vapor concentrating in the lower atmosphere. Since moist air is less dense than dry air, this creates greater instability, leading to stronger updrafts in developing storms and more intense tropical storms and hurricanes. However, this low-level moisture is not effectively transported to high altitudes, resulting in warmer and drier conditions aloft and stronger high pressure in the middle and the upper troposphere. This high pressure aloft forces thunderstorm activity to concentrate in time and space, resulting in fewer tropical cyclones--but the increased moisture at low levels allows more efficient intensification once a tropical storm is spawned. "Thus tropical cyclone intensity increases at the expense of tropical cyclone frequency", the authors wrote. In an interview at, Kang said, "In a warmer year, stronger but fewer tropical cyclones are likely to occur. In a colder year, on the other hand, weaker but more tropical cyclones." Many climate models also predict fewer but more intense tropical cyclones in a future warmer climate--for example, Knutson, T. R. et al., 2010, "Tropical cyclones and climate change", which projected intensity increases of 2 - 11% by 2100. The "official word" on climate, the 2013 IPCC report, predicts that there is a greater than 50% chance (more likely than not) that we will see a human-caused increase in intense hurricanes by 2100 in some regions. The 2014 U.S. National Climate Assessment found that "the intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.”

While it is good news that warming of the oceans may potentially lead to fewer hurricanes, this will probably not decrease the total amount of hurricane damage if the strongest storms get stronger. Damage done by a hurricane increases by somewhere between the second and third power of the wind speed, so just a 10 mph increase in winds can cause a major escalation in damage. According to Pielke et al., 2008, over the past century, Category 3 - 5 hurricanes accounted for 85% of U.S. hurricane damage, despite representing only 24% of U.S. landfalling storms. Category 4 and 5 hurricanes made up only 6% of all U.S. landfalls, but accounted for 48% of all U.S. damage (if normalized to account for increases in U.S. population and wealth.) This study also found that hurricane damages in the U.S. were doubling every ten years without the effect of climate change, due to the increases in wealth and population. If we add in an increase in the frequency of the strongest storms, combined with storm surges that will be riding inland on top of ever-increasing sea levels due to global warming, the damage math for coastal regions gets very impressive for the coming decades.

Nam-Young Kang, James B. Elsner, "Trade-off between intensity and frequency of global tropical cyclones", Nature Climate Change, 2015; DOI: 10.1038/nclimate2646

Pielke, R.A, et al., 2008, "Normalized Hurricane Damage in the United States: 1900 - 2005," Natural Hazards Review, DOI:10.1061/ASCE1527-6988(2008)9:1(29)

Hurricanes and Climate Change: Huge Dangers, Huge Unknowns, my 2013 blog post

The Atlantic remains quiet
High wind shear and dry, sinking air continue to dominate the tropical Atlantic, and none of the reliable models for predicting tropical storm formation show a tropical depression or tropical storm forming over the next five days. However, the models are showing that the remains of an old cold front extending from Florida's Gulf Coast to the waters offshore of North Carolina could serve as the focus of the development of a low pressure area capable of transforming into a tropical storm, early next week. Anything that does form along this front would move northeastwards, out into the open Atlantic, and not be a significant threat to any land areas.

Jeff Masters

State of the Climate Report: Warm and Warmer (except for eastern North America)

Published: July 17, 2015
Although the tropical Atlantic is heating up slightly with the appearance of a Cape Verde wave (see this morning’s tropical roundup post), we also have some toasty news on the national and global front. With our planet showing more and more symptoms of running a fever, the annual State of the Climate reports make for compelling lab results that confirm the diagnosis. This year’s State of the Climate report was released on Thursday as part of the July issue of the Bulletin of the American Meteorological Society. Like a mini-IPCC assessment, this year’s annual report--compiled by NOAA’s National Centers for Environmental Information--involved 413 authors and 17 editors from 58 countries who reviewed and synthesized a vast body of data on what’s happened to our Earth system in the past year, from greenhouse gas increases to sea level rise.

The 2014 State of the Climate report makes it plain that last year was a landmark in global warming. The record high in globally averaged temperature (a mark almost certain to be topped in 2015) got plenty of press, but other records were set as well:

• Carbon dioxide, methane, and nitrous oxide—three of the most important human-produced greenhouse gases—all reached their highest global concentrations since records have been kept.

• More than 20 nations reported their warmest year on record, as did the continent of Europe. The only large land area with below-average temperatures for the year (apart from western Siberia) was eastern North America.

• Sea surface temperatures and global sea level both reached record highs, continuing the trends of recent years.

• The extent of summertime Arctic sea ice remained well below its 1980s – 1990s average, though the ice loss in 2014 was less dramatic than in several years of the past decade. Meanwhile, Antarctic sea ice set new monthly extent records in each month from April to November, and the single largest extent on record was observed on September 20. It’s important to note that this wintertime ice growth around Antarctica has much less effect on climate than the summertime loss in the Arctic, largely because the Arctic loss occurs when more sunshine has a chance to be absorbed by open water.

More highlights from the report can be found in a NOAA news release and in the report itself.

Warmest June nights on record for contiguous U.S.
NOAA’s summary of June climate, also released on Thursday, revealed that last month was the second warmest June across the 48 contiguous states, beaten only by June 1933. And nighttime didn’t offer much relief.

Figure 2. Daily minimum temperatures averaged across the contiguous U.S. for June soared well above the previous record, set in 2010, and more than 1°F above any other year in records extending back to 1895. Image credit: NOAA/NCEI.

Figure 3. State-by-state rankings of temperature (top) and precipitation (bottom) for June 2015. Image credit: NOAA/NCEI.

Averaged across the nation, last month saw the warmest minimum temperatures of any June on record (see Figure 2). In Cheyenne, Wyoming, each night during the entire month saw a low temperature above the norm. June’s balmy nights were largely a result of the cloudiness and rich low-level moisture that prevailed over much of the country, keeping lows from dipping to their usual values. In the western U.S., scorching days accompanied the warm nights: more than 150 western cities broke all-time record highs for June. The states of California, Oregon, Washington, Idaho, and Utah all notched their warmest Junes on record (Figure 3). This Climate Central analysis will show you how much your own state’s summer nights have warmed in the last few decades.

June was also very damp across much of the country (see Figure 2). The Midwestern triad of Illinois, Indiana, and Ohio all experienced their wettest Junes on record; Illinois had its all-time second-wettest month (9.30”, behind only the 9.62” of September 1926). The downpours put a damper on agriculture, with many plantings delayed or compromised. Up to 5 percent of Indiana’s corn and soybean production was lost in June. “We went from a well above-normal crop to a very discouraging, below-normal crop," said Purdue Extension economist Chris Hurt at a briefing on June 26. As of July 13, about a quarter of Indiana corn and soybean crops were rated as poor or very poor.

Figure 4. Cornfields across Jay County in eastern Indiana were doused with heavy rain during the week of June 22. Image credit: Purdue University Agricultural Communication photo/Darrin Pack.

Northeast stays relatively cool
Missing out on the heat in June were Michigan and northern New England, where temperatures ran well below average for the month. As one might expect with plenty of clouds and rain, some states had an unusually compressed temperature range. In Pennsylvania, June’s average daily highs were the 37th coolest on the record, but the daily lows were the 7th warmest. Areas northeast of Pennsylvania are finding it especially tough to warm up this year, even with all the winter snow long gone. The first half of 2015 was among the top 20 coldest January-to-June periods on record for New York and all the New England states. This month, temperatures are running cooler than average across most of the country east of the Rockies, in keeping with the warm-west/cool-east pattern that’s been so persistent for the past year-plus. Meanwhile, the Pacific states continue to roast, including California, with this year to date warmer than all previous Jan-Jun periods in California, Oregon, Washington, and Nevada (see Figure 5).

Figure 5. Average temperatures across California for the period January through June 2015 topped the previous record for the first half of the calendar year, which had been set in 2014. Image credit: NOAA/NCEI.

Heat and drought across the Caribbean into South Florida
Along with the Pacific states, Florida is also cooking: the year to date is the fourth warmest on record for the Sunshine State. In particular, South Florida and the Caribbean have been extremely hot and dry. It was the driest June in 81 years of recordkeeping in Stuart, Florida, and in 110 years of records at Coloso, Puerto Rico. Strict water rationing is now in effect across eastern Puerto Rico: in one location, water is turned off for 48 hours and then on for 24 hours. According to the NWS office in San Juan, El Niño tends to bring the north Caribbean ample moisture during the normally dry months of winter and spring, but below-average rainfall from May through November.

I’ll have a special report this weekend on progress in severe weather modeling and prediction. Jeff Masters and I will both be back on board next week. Have a great start to your weekend!

Bob Henson

Germany Breaks its All-Time Heat Record

Published: July 6, 2015
Germany broke its all-time heat record on Sunday July 5, when the mercury soared to 104.5°F (40.3°C) at the official Kitzingen station in Bavaria. According to the German weather service's Facebook page, the record is now confirmed as official. The previous official national heat record recognized by the German meteorological agency (DWD) was 104.4°F (40.2°C), set in July 1983 and matched in August 2003. Numerous cities in Germany set all-time heat records over the weekend, including Saturday's 100.2°F (37.9°C ) reading at Berlin's Dahlem station, which has a very long period of record going back to 1876. Frankfurt beat its all-time heat record on Sunday--both at the airport (38.8°C) and downtown (39.0°C). Thanks go to weather records researcher Maximiliano Herrera and Klimahaus' Michael Theusner for these stats. According to an analysis of DWD observing station data done by Dr. Theusner, 131 of 492 stations in Germany set an all-time heat record during the July 2 - 5 heat wave, and another 7 tied their previous record.

Figure 1. A young boy jumps from a 7.5 meter platform at a crowded outdoor pool during a record heat wave in Frankfurt, Germany, Friday, July 3, 2015. (AP Photo/Michael Probst)

More near-record heat on the way
Germany has joined four other nations that have set all-time July national heat records this month: the Netherlands, the U.K., Thailand, and Colombia. Intense heat will continue over portions of Europe the next three days, with more national July heat records at risk. The fiercest heat will be over Poland on Monday, over Germany, Switzerland, and Austria on Tuesday, then shift to Southeast Europe on Wednesday. High temperatures close to the highest values ever measured can be expected in all these locations. For reference:

Poland's all-time hottest temperature is 104.4°F (40.2°C), measured on July 29, 1921 at Proszkow.

Switzerland's all-time hottest temperature is 106.7°F (41.5°C), measured on August 11, 2003 at Grono.

Austria's all-time hottest temperature is 104.9°F (40.5°C), measured on August 8, 2013 at Bad Deutsch-Altenburg.

Liechtenstein's all-time hottest temperature is 99.3°F (37.4°C), measured on August 13, 2003 at Ruggel.

Andorra's all-time hottest temperature is 101.3°F (38.5°C), measured on July 16, 2005 at Andorra La Vella.

Climate Change Playing a Significant Role in 2015 European Heat Wave
According to a press release by Climate Central, an international team of scientists from Oxford University, KNMI, Red Cross Red Crescent Climate Centre, along with regional partners from CNRS and MeteoSwiss says it is virtually certain that climate change increased the likelihood of the ongoing heat wave stretching across much of Europe. The risk increased by a factor of two or more over a large part of Europe, and up to more than a factor of four in some of the hottest cities. For example, the 3-day heat wave over the past three days in Mannheim, Germany would have been a 1-in-100 year event around the year 1900. It is now likely to happen roughly 1 in 15 years, thanks to climate change. The results are a part of the developing field of “weather attribution” that uses observational weather and climate data, weather forecasts and climate models.

Jeff Masters
Categories:Heat Climate Change

Pakistan's Deadliest Heat Wave on Record Kills at Least 800

Published: June 24, 2015
The death toll from a brutal heat wave in Pakistan rose to 830 on Wednesday, making it Pakistan's deadliest heat wave in recorded history. Most of these deaths--at least 770--occurred in Pakistan's largest city, Karachi. According to statistics from EM-DAT, the International Disaster Database, Pakistan's previous deadliest heat wave was in 1991, when 523 people died.

Death Tolls from the 5 Deadliest Heat Waves in Pakistan's History
1) 2015: 830+
2) 1991: 523
3) 2014: 248
4) 2003: 200
5) 1953: 111

Figure 1. Pakistanis receive ice outside a hospital during heatwave in Karachi on June 24, 2015. A state of emergency was declared in hospitals. Image credit : RIZWAN TABASSUM/AFP/Getty Images.

Figure 2. Temperatures in Karachi, Pakistan from June 11 - June 24, 2015 show that the heat wave peaked on June 20, with a high temperature of 112.6°F (44.8°C.) The heat index was as high as 121°F.

The worst of the heat is over for Pakistan
The past week saw an unusually long string of very hot days with temperatures that did not cool off at night in Pakistan. The heat wave peaked on Saturday June 20, when the high temperature hit 112.6°F (44.8°C) in Karachi; the heat index peaked at a dangerously high 121°F. According to the Pakistan Meteorology Department, Karachi's all-time high temperature was 118°F (47.8°C) on May 9, 1938. A tropical depression associated with the approaching southwest monsoon pushed ashore along the border of Pakistan and India on Tuesday, bringing thunderstorms and cooler weather. Wednesday's high reached only 98°F in Karachi, breaking a streak of six consecutive days when the temperature hit 103°F or higher. The previous longest streak of 103°F+ temperatures during the past fifteen years was three consecutive days, which occurred most recently in 2006. Temperatures failed to dip below 85°F at night during the streak of 103°F days over the past week; very warm nights are associated with high mortality during intense heat waves, since there is no chance for the body to gain an overnight respite. High temperatures are expected to rise to 103°F again in Karachi on Thursday, but then cool to the upper 90s over the weekend--about ten degrees Fahrenheit cooler than last weekend's temperatures. The cooling rains from the southwest monsoon are likely to arrive in Karachi by mid-July, and the circulation associated with the monsoon should insure that the region will not see any more temperatures this summer as high as were recorded last weekend. If the death toll from the 2015 Pakistan heat wave rises above 1,030, it will join this year's May 2015 heat wave in India as one of the ten deadliest heat waves in world history.

Figure 3. Progress of the monsoon towards Pakistan as of June 23, 2015 (green line) has been about a week slower than its usual pace. Karachi, Pakistan usually sees the monsoon move through during the second week of July. Image credit: India Meteorological Department .

A deficient monsoon predicted, but above-average rains so far
The atmospheric circulation patterns brought on by an El Niño event usually cause much reduced monsoon rains in India. With the current moderate El Niño event is forecast to intensify this summer, the India Meteorological Department (IMD) is forecasting only a 7% chance of near-average rains during the 2015 summer monsoon period, and a 93% chance of below average or well below average rains. IMD's best estimate is that 12% less rain than usual will fall. However, during the first half of June, monsoon rainfall was 11% above average for India as a whole.

Climate change and the monsoon
This year's deadly heat waves in India and Pakistan were made much more probable by the fact that Earth is experiencing its hottest temperatures on record--the January - May 2015 period was the planet's hottest such period on record. The planet's record heat contributed to unusually warm ocean temperatures off the coast of Pakistan, which were about 1°C (1.8°F) above average this week. Warmer oceans make hotter heat waves over adjoining land areas more likely. According to the India Meteorological Department, a warming climate increased heat waves in India by a third between 1961 to 2010. As the planet continues to warm due to human-caused global warming, heat waves will become more frequent and more intense, and heat-related deaths will soar unless we take strong measures to adapt. An April 2015 paper published in Regional Environmental Change, Intensification of future severe heat waves in India and their effect on heat stress and mortality, warned that "heat waves are projected to be more intense, have longer durations and occur at a higher frequency and earlier in the year. Southern India, currently not influenced by heat waves, is expected to be severely affected by the end of the twenty-first century." Perhaps a bigger concern for India and Pakistan with climate change is drought, though. Many climate models show that climate change might increase the average rainfall in India and Pakistan from the monsoon, but when dry years occur, the hotter temperatures accompanying the dry years will drive much more intense droughts capable of causing significant challenges to growing food.

Jeff Masters
Categories:Heat Climate Change
About the Blogs
These blogs are a compilation of Dr. Jeff Masters,
Dr. Ricky Rood, and Angela Fritz on the topic of climate change, including science, events, politics and policy, and opinion.