Why Heavy Rain Events are Becoming More Common

Torrential rain events and the flooding they cause are nothing new. Global warming, however, is helping to make them more likely.

Heavy rainfall trends in NYC. Credit: Climate Central

According to the most recent National Climate Assessment, heavy precipitation events have increased in both frequency and intensity across the United States. While there are seasonal variations with different regions, the greatest increases have been observed in the northeast.

Climate scientists attribute this increase in heavy precipitation to our warming world. As greenhouse gases warm the atmosphere, the air is able to hold more water vapor. More specifically, according to the Clausius–Clapeyron relation, for every increase of 1°F, the saturation level of the atmosphere increases by about 4%. That means there is more evaporation from oceans, rivers, and lakes, and therefore more water vapor available to condense and fall as precipitation.

Heavy rain events have a number of consequences, including an increased risk of both flash floods and river floods. This, in turn, is a threat to life and property. Over the long-term, it also affects insurance rates and property values. According to NOAA, individual billion-dollar flooding events (excluding tropical cyclones) in the U.S. have added up to $39 billion in losses since 2010.

As our global temperature continues to rise, experts say we should expect to see more extreme rain events, even in areas where overall precipitation is projected to decrease. In other words, when it rains, it will likely pour.

Downpours have been getting more frequent and intense across the US. Credit: Climate Central and NCA4

Hurricane Names Harvey, Irma, Maria and Nate Retired

There will never be another hurricane by the name of Harvey, Irma, Maria, or Nate. The World Meteorological Organization (WMO) has announced that it is officially retiring these names from its list of Atlantic cyclones.

The WMO is responsible for naming tropical storms and hurricanes around the world.  It maintains a set of six rotating lists for each hurricane-prone region. After a six-year cycle, names are re-used.  Names are only retired when a storm was particularly noteworthy – causing a large number of fatalities or an extraordinary amount of damage.

The 2017 Atlantic hurricane season was brutal, but four storms were particularly destructive. Hurricane Harvey, a category-4 storm, made landfall in Texas and dumped a record-breaking amount of rain in the Houston area, unleashing catastrophic flooding. Irma clobbered the Florida Keys as category-4 hurricane, but its impacts were felt throughout the entire Sunshine state. Hurricane Maria made landfall in Puerto Rico as a high end category-4 storm and knocked out power to more than 90% of the island for months. Nate hit the US Gulf Coast as a category-1 storm, but most of its deadly impacts were felt in Central America when it was still a tropical storm.

According to the National Hurricane Center, 86 storm names have been retired since the current naming system began in 1953. This year marks the fifth time that four or more names have been retired from a single season. Three of those -1955, 1995, and 2004 – each had four names retired. In 2005, five names were retired – the most ever from one hurricane season.

Starting in 2023, when last year’s list is recycled, the names Harvey, Irma, Maria, and Nate will be replaced by Harold, Idalia, Margot, and Nigel. Some other notable retired Atlantic Basin storm names include: Andrew, Katrina, Irene, and Sandy.

The 2018 Atlantic hurricane season officially begins on June 1.

Four names from the 2017 Atlantic hurricane season are retired. Credit: WMO

National Drought Update: Early Spring 2018

The northeastern United States received copious amounts of precipitation from the four nor’easters that blasted the region this month. Much of the rest of the country, however, has been parched.

According to the latest report from the U.S. Drought Monitor, 31% of the nation is dealing with some form of drought. While this number represents a slight improvement for California, the situation in the southern plains and the southwest has been getting worse. Parts of the Texas Panhandle, western Oklahoma and southwestern Kansas are in exceptional drought, the worst possible category.

Drought conditions have also been building in parts of the southeast. In Florida, according to the state’s Forest Service, dry conditions have fueled more than 1000 wildfires across the peninsula since the beginning of the year.

The US Drought Monitor is a weekly publication produced by a partnership of government agencies, including the National Drought Mitigation Center, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.

Credit: US Drought Monitor

2017: Third Warmest Year on Record in US

2017 was the third-warmest year ever recorded in the continental United States. Only 2012 and 2016 were warmer.

The average annual temperature of the lower 48 states, according to a report by NOAA’s National Centers of Environmental Information, was 54.6°F. That is 2.6°F above the 20th-century average. 2017 also marked the 21st consecutive year that the annual average temperature for the contiguous US was above its long-term norm. That means the last time the US had a normal to below normal annual temperature was 1996.

From coast to coast, for the third year in a row, every state posted an above-average annual temperature. Five states – Arizona, Georgia, New Mexico, North Carolina, and South Carolina – had their warmest year on record. This was despite the unusually cold conditions that dominated the eastern part of the country in December.

The year was also notable for its unusual number of weather and climate disasters that each totaled more than $1 billion in damages. In all, sixteen such events collectively caused $306 billion in direct costs – a new US record. Sadly, they also claimed the lives of at least 362 people across the country. These incidents included drought, wildfire, floods, severe storms, and three major landfalling hurricanes.

The exceptional warmth of 2017 was independent of El Niño. In fact, ENSO neutral conditions prevailed for most of the year and La Niña – the cool counterpart of El Niño – developed in the autumn.

Weather records for the contiguous United States date back to 1895.

Credit: NOAA

Credit: NOAA

La Niña is Back and Likely to Stick Around Through the Winter

La Niña, the cooler counterpart of El Niño, has returned for the second year in a row.

It is a natural event associated with the larger El Niño-Southern Oscillation (ENSO) climate pattern and is marked by cooler-than-average ocean water in the central and eastern tropical Pacific. More specifically, a La Niña event is declared when sea surface temperatures in that region are at least 0.5°C below average and accompanied by a consistent atmospheric response. This includes more clouds and rain over the western Pacific and less over the central part of that basin. Stronger than average upper-level wind is also a key atmospheric indicator.

The relatively cool water associated with La Niña creates an area of high pressure over the Pacific and pushes the jet stream northward. This, in turn, affects weather patterns around the globe.

In the US, a La Niña event typically brings the southern states conditions that are warmer and drier than normal. The northern tier, on the other hand, usually experiences below average temperatures with the northwest and Great Lakes regions receiving above average precipitation.

That said, every La Niña event is different. There are also other atmospheric factors, such as blocking patterns, which can influence the weather.

According to NOAA, there is a 65%-75% chance of weak La Niña conditions continuing through the winter months.

Typical Winter La Niña jet stream pattern over North America. Credit: NOAA/Climate Prediction Center.

Massive Federal Science Report Says Humans Cause Climate Change

The Fourth US National Climate Assessment (NCA4) was released on Friday. It clearly states that climate change is real, it is happening now, and human activities are the main cause.

The first volume of the assessment – the Climate Science Special Report – says the average global temperature has increased 1.8°F (1°C) during the past 115 years (1901-2016). “This period is now the warmest in the history of modern civilization,” according to the report. It also says that “it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century.” Going even further, the report concludes, “there is no convincing alternative explanation supported by the extent of the observational evidence.”

With a focus on the US, the report says the average annual temperature in the contiguous forty-eight states has increased by 1.2°F (0.7°C) since 1986, relative to the previous century. It is projected to increase 2.5°F (1.4°C) by 2050.

In addition to warming, other aspects of climate change are highlighted in the massive report. One of these is sea level rise. Since 1900, the average global sea level has gone up 8 inches. Of that total, a 3-inch rise has occurred since 1993. This rate of rising, according to the report, “is greater than during any preceding century in at least 2,800 years.”

Moving forward, all projections show sea level continuing to rise. An increase of several inches is likely in the next fifteen years and 1 to 4 feet is estimated by 2100. A rise of as much as 8 feet by the end of the century, however, “cannot be ruled out”, the report warns. This is especially true if the ice sheets in Greenland and Antarctica prove to be more sensitive to rising temperatures than expected. In cities along the Gulf Coast and Eastern Seaboard, where daily tidal flooding is already a problem, sea level rise is forecast to be even higher than the global average.

The report also contains details on how extreme weather is changing across the US. For example, heavy rainfall events are ”increasing in intensity and duration” nationwide with the biggest increases happening in the northeast. In the west, the incidence of large forest fires has been rising since 1980 and is expected to increase even further in the coming years. Heat waves, unsurprisingly, have also become more frequent while cold waves have become less frequent.

Looking beyond the next few decades, the NCA says the magnitude of climate change depends on the amount of greenhouse gases that are added to the atmosphere. The level of carbon dioxide in the air today has already passed 400 parts per million, a number not seen in 3 million years. If emissions are not reined in, the average global temperature could increase by as much as 9°F (5°C) by the end of this century. According to the report, “the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts.”

Mandated by Congress under the Global Change Research Act of 1990, this exhaustive climate report was produced by hundreds of experts from government agencies as well as academia and was peer-reviewed by the National Academy of Sciences. Published every four years, it is considered this country’s most authoritative statement on climate change.

Its findings, however, are in stark contrast to the words and actions of the Trump Administration. The President has called climate change a “hoax” and in June announced that he is withdrawing the US from the Paris Climate Agreement – an international accord that aims to reduce greenhouse gases and limit global warming to 2°C (3.6°F). The US and Syria are now the only two countries not part of the historic agreement.

Global annual average temperature (left) and surface temperature change for the period 1986–2016 relative to 1901–1960. Credit: NCA4

Road Trip Highlights US Environmental History and Shows Big Changes are Possible

Last week, I was in Pittsburgh, PA to serve as a Mentor at a Climate Reality Project training event. Having never been in that part of the country before, I spent a few extra days to explore the area. The overall experience felt like a road trip through US environmental history and was a great reminder that large-scale changes are possible, especially in this era of climate policy backpedaling.

First stop: Donora, PA. This Pittsburgh suburb was the site of the “Killer Smog of 1948”. As the longtime home of the Donora Zinc Works Factory and the American Steel and Wire Plant, smoke-filled skies were not unusual here in the early part of the 20th century. In October 1948, however, the air turned deadly. An inversion layer, a weather phenomenon where the temperature in the atmosphere increases with height instead of decreasing, trapped emissions from the factories. The sulfuric acid, nitrogen dioxide, fluorine, and other poisonous gases created a thick, yellowish smog. It hung over the area until the weather pattern changed five days later. As a result, twenty-six people died and thousands of others became ill.

This tragedy garnered national attention and spurred federal regulations on air pollution. In 1955, Congress provided funding for pollution research and later passed the Clean Air Act of 1963. In 1970, the EPA was created and Congress passed the Clean Air Act Amendments, which established national air quality standards.

Donora is proud of their role in this change in national environmental policy. Outside of their local Historical Society/Smog Museum is a sign that says “Clean Air Started Here”.

Another highlight of this trip was Cuyahoga Valley National Park in northeastern Ohio. Established as a National Recreation Area in 1974 and upgraded to a National Park in 2000, it reclaimed and now preserves the natural landscape along twenty-two miles of the Cuyahoga River between Akron and Cleveland, OH. While relatively small, the river is an icon of American environmental history.

Starting in the late 1800s, the river became highly industrialized. For more than a century, the steel mills and factories that lined its banks dumped untreated waste directly into the river. The Cuyahoga became so polluted that it caught on fire thirteen times.

The last time was June 22, 1969, when sparks from a passing train ignited the oil and debris floating in the water. This fire, while not the largest or deadliest in the river’s history, caught the attention of Time Magazine and became national news. Appearing in their August 1 issue, the article described the Cuyahoga as a river that “oozes rather than flows”.

During the late 19th and early 20th century, river fires were common and seen as the price of industrial progress and prosperity. By the 1960’s, however, that way of thinking was starting to change. The country was becoming more environmentally aware and the Cuyahoga River fire put a national spotlight on the need to protect waterways from industrial pollution. The event helped to galvanize the Water Quality Improvement Act of 1970 and the Clean Water Act of 1972.

In the years since, the Cuyahoga River has made an amazing comeback. Bald Eagles – a symbolic emblem of this country – have returned to fish its waters and nest along its banks. In 1998, it was designated as an American Heritage River to recognize its historical significance.

Today, our environmental challenge is the carbon pollution that drives climate change. Its solution, as with conservation issues in the past, lies with policy adjustments. While these types of large changes can sometimes seem impossible, history reminds us that they are not. All that is required is the will to act. As Nelson Mandela once said, “It always seems impossible until it’s done”.

Cuyahoga River, past and present. Credit: Cleveland State University Library

Wildfire Outbreak in Northern California

Northern California is ablaze with wildfires.

As of Thursday, according to CalFire, 22 wildfires are burning in the Golden State. They have scorched over 190,000 acres and forced the evacuation of entire neighborhoods. Officials say at least 26 people have been killed and more than 400 are missing. In terms of property damage, they conservatively estimate that 3,500 homes and structures have been destroyed.

The smoke and ash from these fires are also causing widespread air quality issues. In the Bay Area, well outside of the burn zone, air quality reached historically poor levels this week.

These huge fires are largely the result of climate whiplash. California has distinct wet and dry seasons, but they have been extreme recently. After years of drought, this winter brought the state record amounts of precipitation that spurred explosive new plant growth. Then during the summer, which was the state’s warmest on record and unusually dry, all that vegetation turned to tinder.

Making matters worse, the region’s seasonal winds known as the Diablo Winds began blowing over the weekend. They reportedly reached speeds as high as 70mph in some areas. Blowing east to west, these winds warm from compression as they flow downslope from the mountains towards the coast and dry out vegetation even further. They also fan the flames of any fire already burning and can cause it to spread very quickly.

The Diablo Winds are essentially the same type of air current as the famous Santa Ana winds in southern California. They only really differ in location and name. The Diablo Winds are named for Mount Diablo in the East Bay area and the Santa Ana Winds are the namesake of Santa Ana Canyon in Orange County.

Wildfires are not unusual in California, but this outbreak is considered one of the worst in state history. The exact cause of the fires is still unknown.

Wildfire burns near Glen Ellen, CA. Credit: The SF Chronicle

Hurricane Nate Slams Gulf Coast

Hurricane Nate, the 14th named storm of the 2017 Atlantic Hurricane season, made two landfalls along the US Gulf Coast this weekend. The first was near the mouth of the Mississippi River in Louisiana and the second was near Biloxi, Mississippi.

Coming ashore with 85mph winds, this category-1 hurricane generated a significant storm surge that swamped parts of the region from Louisiana to the Florida Panhandle. One of the hardest hit areas was Pascagoula, MS where a storm surge of 6.3 feet was reported. The storm also downed trees and caused widespread power outages.

Moving inland, Nate was soon downgraded to a tropical depression. However, it still spawned a number of destructive tornados from Alabama to North Carolina. They ranged in strength from EF-0 to EF-2.

Nate was the first hurricane to make landfall in Mississippi since Katrina in 2005.

Credit: NOAA/NASA GOES

Hurricane Maria Devastates Puerto Rico

Hurricane Maria, the 13th named storm of this Atlantic Hurricane season, made landfall in Yabucoa, Puerto Rico on Wednesday morning. It was the strongest storm to hit the US Territory since 1928.

Coming ashore with sustained winds measured up to 155mph, Maria was classified as a high-end category-four hurricane. Its powerful winds sheared roofs and balconies off buildings, uprooted trees, and toppled power lines. In addition, the storm’s torrential rain unleashed devastating flooding across the island. More than 30 inches of rain was reported near Caguas, PR.

Local authorities say the entire island, home to 3.5 million people, is without power. They do not expect it to be fully restored for four to six months. This unusually lengthy timeframe is largely due to the fact that Puerto Rico is an island with rugged terrain and an electrical grid that has been crumbling for years from a lack of maintenance. The Puerto Rico Electric Power Authority, the territory’s sole provider of electricity, effectively filed for bankruptcy in July.

Before making landfall in Puerto Rico, Maria roared through the Caribbean and reached category-five strength. It battered several other islands, including the US Virgin Islands, which were still reeling from the devastation caused by Hurricane Irma less than two weeks ago. As of Thursday, the death toll from Maria stands at seventeen. But sadly, this number is expected to increase as search and rescue efforts continue across the region.

Maria was the third category-four hurricane to hit the US, or one of its territories, in less than a month. In 166 years of record keeping, this has never happened before.

Hurricane Maria moves across Puerto Rico. Credit: NOAA/NASA