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Acidifying Waters Put Dungeness Crabs at Risk
When it comes to American culinary institutions, the Dungeness crabs that are hauled ashore from California to Washington state every winter season are the crustacean equivalents of apple pie.
The bountiful crab meat is a holiday staple in the San Francisco Bay Area and beyond. When crabbing was suspended in the fall by an algae outbreak, journalists flocked to docks to produce lead news stories — just as they did when crabbing was restricted following a 2007 oil spill.
Research published this month could give a crab connoisseur a case of acid reflux.
Dungeness crabs for sale in Seattle.
Scientists reported in the journal Marine Biology that ocean acidification, which is caused when carbon dioxide pollution dissolves into oceans, can kill and stunt young crabs, potentially jeopardizing whole populations.
“It’s something that’s projected into the future, but you don’t want to wait until a crisis,” John Mellor, a Dungeness crab fishermen who docks his boat in San Francisco, said during an interview last week in Washington, D.C., where he was meeting with lawmakers and others. “I’m here to try to convince people to give money for research.”
Scientists grew eggs and larvae from Puget Sound crabs in water containing pH resembling current and future conditions. They reported that more acidic seawater slowed the development of embryos and larvae and caused an “appreciable” number of larvae to die.
Ocean acidification is caused by carbon dioxide pollution — the same pollutant from fuel burning and deforestation that changes the climate. After carbon dioxide dissolves into seawater, it undergoes chemical reactions that change the pH and remove chemicals needed by corals, shellfish and other creatures to produce rigid body parts.
West Coast waters are more prone to acidification than other regions. As the threat of acidifying waters weighs on the minds of crabbers, those who grow shellfish are already being directly affected. The Pacific Northwest’s oyster growing industry has been experiencing substantial losses of young shellfish linked to acidification since 2005.
“The really tough situation with the shellfish industry on the West Coast was the first major alarm bell,” said Jeff Watters, director of government relations at the nonprofit Ocean Conservancy. “That was the first moment where you literally had an industry who said, ‘Holy cow, this could shut us down.’”
Seth Miller, a Smithsonian Environmental Research Center scientist who wasn’t involved with the new study, said it added Dungeness crabs to the “long list of crustaceans and other invertebrates that will likely be negatively impacted” by ocean acidification during their larval stages.
“If Dungeness larvae develop slowly under acidified conditions, they're likely going to struggle even more when you layer on other climate-related stressors like rising temperatures,” Miller said.
Miller said the research provides a “first look” at how acidification could affect crab populations. Scientists don’t know whether acidification is affecting crab populations already — nor do they precisely know how it could affect them in the future.
“We don’t have any direct evidence that they’re currently being affected, except that in some places we see a decreased survival under conditions that currently exist in some places,” said Paul McElhany, a NOAA ecologist who participated in the new study.
“We’re completely into new territory,” McElhany said. “Carbon dioxide has never changed this rapidly as far as we can tell.”
The West Coast’s crab population is a large one, occupying vast territory in the Pacific Ocean, raising hopes that it may harbor enough genetic variety to help it withstand environmental tumult, such as acidification. But how resilient it will actually be remains unknown.
“We’re only able to do experiments on a few life stages for a certain amount of time,” McElhany said. “So the question of the role that diversity might play in potential evolutionary response — that’s something that’s really just unknown at the moment.”
The coastal Washington state district of Rep. Derek Kilmer, a Democrat, contains thousands of people whose livelihoods depend on shellfish. He has introduced legislation designed to spur more research through federal grants and innovation prizes.
“I think there’s a real concern that, as you see changing ocean chemistry, that that’s a threat to their livelihood,” Kilmer said. “We’re trying to shine a bright light on the problem.”
Further research could help determine whether the crabs could evolve quickly enough or learn to adapt to changing pH concentrations. Such research may provide clues as to whether anything could be done to help crabs withstand acidification — apart from drastically curbing fossil fuel burning and deforestation, which is the goal of a new United Nations climate change treaty.
“This bill is not going to solve all the world’s problems,” Kilmer said. “To me, this is one of many things that have to happen.”
U.S. Leads Globe in Oil Production for Third Year
The U.S. led the world last year in producing both oil and gas, federal government estimates published Monday show, even as the country committed to cutting greenhouse gas emissions.
The U.S. was the globe’s leading producer of crude oil for the third year in a row in 2015. Government estimates show that crude oil production has continued to grow across the country, from nearly 8 million barrels of oil per day in 2008 to about 15 million in 2015. The U.S. produced about 14 million barrels per day in 2014.
An oil refinery in Texas.
Credit: Roy Luck/flickr
Thanks to the fracking boom, which unlocked previously hard-to-reach shale oil and gas, the U.S. surpassed Saudi Arabia and Russia to become the world’s leading producer of oil in 2013. The U.S. became the top natural gas producer in 2011, and has led the world in both oil and gas production together for four years in a row.
As oil prices remain low, U.S. oil production is expected to decline slightly in 2016 and 2017, falling to about 14.5 million barrels per day, the estimates show. U.S. Energy Information Administration analyst Linda Doman said the decline is not likely to mark 2015 as an all-time peak in U.S. oil production, which could pick up if and when oil prices climb again.
The uptick in crude production last year came as the U.S. helped strike the Paris Climate Agreement, which aims to keep global warming from exceeding 2º C (3.6º F) above pre-industrial levels. The Obama administration also killed the Keystone XL Pipeline last year, partly because the oil it would carry would worsen climate change.
Climate scientists say U.S. oil and gas production trends and the administration’s “all of the above” energy strategy, which includes encouraging fossil fuels and renewables production, don’t square well with its climate policy.
“The U.S. can lead the world in both climate action and crude oil production, but not for long,” said Jonathan Koomey, a research fellow at the Steyer-Taylor Center for Energy Policy and Finance at Stanford University. “To preserve a stable climate we need to phase out fossil fuel consumption as fast as possible, starting as soon as possible. This is why the administration's ‘all of the above’ energy strategy is incoherent. We have to stop building new fossil fuel infrastructure and start retiring existing infrastructure.”
The White House did not respond to a request for comment on Monday.
Penn State University climate scientist Michael Mann said the U.S. must embrace renewable energy more fervently and decarbonize the economy.
“It is necessary both for avoiding catastrophic climate change and retaining our international economic competitiveness,” he said. “The good news is that we’re moving in that direction, though — as we can see with these latest numbers — the benefits of very recent climate policies enacted under the Obama administration have yet to be fully realized.”
Abrupt Atlantic Ocean Changes May Have Been Natural
Climate change may not have been to blame for an abrupt recent slowdown of a sweeping Atlantic Ocean current, a change that delivered an intense pulse of ocean warming and sea level rise through the Gulf of Maine and elsewhere along the East Coast.
Modeling-based analysis by British scientists, published Monday in Nature Geoscience, concluded that the decline in the Atlantic meridional overturning circulation (AMOC) from 2004 to 2014 was “part of decadal variability of the North Atlantic,” representing a recovery following a previous strengthening of its currents.
Atlantic Ocean currents influence the weather and sea levels.
Credit: John Spade/Flickr
Still, leading scientists warn that greenhouse gas pollution appears to be causing the circulation pattern to slow down, and that it will continue to do so with far-reaching implications for weather and for flood-prone cities and farms around the world.
The findings were based on analysis of data from Met Office weather forecasting models. They were generally welcomed by other scientists, who said they point to the powerful role that the whims of nature can play on the ocean cycle — even as greenhouse gas pollution causes ice sheets to melt, which prior research has shown is causing the circulation to slow overall.
“The decline we’ve seen is much larger than we would have expected just from increasing greenhouse gases over the last decade,” said Tom Delworth, a climate scientist with the National Oceanic and Atmospheric Administration and Princeton University. He wasn't involved with the study.
The AMOC washes warm equatorial waters toward the Arctic and shuffles cold Arctic waters southward, helping to regulate ocean and air temperatures.
Greenhouse gas pollution has caused air temperatures to rise nearly 2°F globally since the Industrial Revolution, warming oceans and causing seas to rise worldwide now by an average of more than an inch per decade. The Atlantic circulation slowdown caused impacts to be especially pronounced along the East Coast, worsening floods and devastating some fisheries.
The slowdown of the Atlantic circulation was particularly pronounced around 2009 and 2010, which research has shown contributed to a frenetic Atlantic hurricane season and to unusually cold winters in parts of North America and Europe. More recently, it may have intensified the January blizzard that briefly shut down New York and other East Coast cities.
As ocean currents go, the AMOC also plays an outsized cultural role in framing conversations about global warming. The effects of its slowdown were fictionalized in the 2004 science fiction movie, “The Day After Tomorrow.” Two years later, links between climate change and the ocean current were explained in the climate change documentary, “An Inconvenient Truth.”
The new paper didn’t attempt to determine the root cause of the cycles that periodically cause the Atlantic circulation to strengthen and weaken. Like other scientists, Laura Jackson, a Met Office scientist who led the research, said “the most likely explanation” was “natural variability.”
“Our results suggest that there hasn’t been a persistent weakening of the AMOC over the last 20 years,” Jackson said. “More years of observations would be required to identify an ongoing trend. This does not change the view that it is very likely that the AMOC will weaken over the 21st century.”
A January blizzard in New York may have been intensified by changes in the Atlantic Ocean's circulation patterns.
Credit: Stacey Bramhall/Flickr
Although the findings were well received overall by other scientists, the suggestion that the recent slowdown represented a “recovery” following a previous speedup triggered some consternation. That’s because it could be seen as diminishing the long-term role of climate change in affecting the circulation.
Michael Mann, a Penn State meteorology professor who contributed to research last year showing the AMOC is weaker now than in the last 1,000 years, said the conclusions of the new paper were “consistent with our findings.”
But Mann described the use of the word “recovery” in the title and abstract of the paper as a “gaffe” that “detracts considerably from what would otherwise be a useful contribution to the peer-reviewed literature.”
Chris Roberts, a Met Office scientist who contributed to the new paper, defended the work by pointing out that the team’s focus was limited to addressing changes that have been observed over the last couple of decades — rather than over recent centuries or into the future.
“Our results do not exclude a longer-term weakening,” Roberts said.
Cities ‘Woefully Unprepared’ for Rising Disaster Risk
By Laurie Goering, Thompson Reuters Foundation
Cities around the world are failing to plan for fast-increasing risks from extreme weather and other hazards, particularly as population growth and surging migration put more people in the path of those threats, the World Bank said.
By 2050, 1.3 billion people and $158 trillion in assets will be menaced by worsening river and coastal floods alone, warned a new report from the Global Facility for Disaster Reduction and Recovery (GFDRR), managed by the World Bank.
"Cities and coastal areas are woefully unprepared for the kind of climate and disaster risk now facing our world," said John Roome, the World Bank Group’s senior director for climate change.
A man pushes his bicycle cart through waist-deep flooding caused by typhoon Linfa at Longos town in Malabon city, north of Manila July 6, 2015.
Credit: REUTERS/Romeo Ranoco
But as cities expand and revamp, they have the opportunity to lower that risk by putting in place more resilient infrastructure and preventive policies, he said.
Those could include everything from restrictions on using too much groundwater – one of the reasons cities from Tokyo to Jakarta are sinking – to planning for more green space, and new schools and apartments set above flood-prone zones.
The problem is that many city officials have no clear idea of the range of disaster risks they face and how serious they could be. Argentina, for instance, has no volcanoes but is affected at times by ash from eruptions in Chile.
And when Malawi was hit by an earthquake in 2009, it came as a surprise. "Not many people think about the African continent and its potential for earthquakes," said Alanna Simpson, a risk management specialist with the GFDRR.
No PhD? Help At Hand
A new open-source disaster risk management tool, called ThinkHazard!, aims to make planning for such threats easier by pulling together information on all potential disaster risks in a country or region, and how they compare.
It looks at hazards including floods, cyclones, droughts, heat waves, fires, earthquakes, tsunamis, volcanic eruptions and landslides.
The tool, aimed at national and city planners, project developers and others, also offers advice on what might work to reduce the risks.
While information on disaster risks already exists, it tends to be in scattered locations and jargon-heavy language, Simpson said.
For an average planner, "you need a PhD to understand if a country has risk and how it might affect your project", she told the Thomson Reuters Foundation.
The new tool, developed by the GFDRR, brings the information together and simplifies it, so that the developer of a road or school in Kenya, for instance, can get a sense of the level of risks their project faces - including threats they may not know about.
Those can be substantial, the disaster experts noted. In Indonesia, the risk of flooding from overflowing rivers is expected to grow 166 percent over the next 30 years, while coastal flooding risk could rise 445 percent, the report said.
Nepal's capital Kathmandu is expected to see a 50 percent rise in earthquake risk by 2045 as more slums and informal buildings go up.
A combination of sea-level rise and sinking of coastal cities – including from excessive extraction of the groundwater beneath them – could drive disaster losses in 136 coastal cities from $6 billion a year in 2010 to $1 trillion a year by 2070, the report said.
But planning now for more big typhoons in Manila, for example, by ensuring new homes are not built on flood plains and keeping drainage canals clear, will pay off, the experts said.
"The decisions we make today are defining the disasters of tomorrow," said Francis Ghesquiere, head of the GFDRR secretariat.
"We have a huge challenge – but also a huge opportunity – to try to make sure the trillions of dollars that will go into new housing, new infrastructure, the extension of cities... do not increase risk exposure but rather reduce it."
Reporting by Laurie Goering; editing by Megan Rowling
Global Warming Will Hit Poorer Countries Hardest
By Fiona Harvey, The Guardian
New evidence that poorer countries will suffer the worst effects of climate change has shown that the number of hot days in tropical developing countries is likely to increase markedly as global warming takes hold.
Solomon Islands is under threat from sea level rise.
It has long been expected that poor people would bear the brunt of climate change, largely because so many more of the world’s poorest live in tropical latitudes whereas, wealthier people tend to live in more temperate regions.
This is inverse to the generally accepted responsibility for climate change, which falls mainly on rich countries that benefited early on from industry, and thus have historically high emissions, compared with poorer countries that have only begun catching up in the past few decades.
It was oniy in 2014 that China's per capita emissions caught up with those of people in the E.U., even after years of above-average economic growth in China.
Those living in the poorest countries also have the most to lose, as so many depend on agriculture, which is likely to be badly affected by temperature rises and an increase in droughts, heatwaves and potential changes to rainfall that may lead to recurrent patterns of floods, droughts and higher intensity storms.
The study, led by the University of East Anglia, is the first to examine the link between cumulative carbon dioxide emissions and more frequent hot days.
Manoj Joshi of the UEA School of Environmental Sciences said: “Many of the poorest people in the world live in tropical latitudes, while many of the world’s wealthiest people live in mid-latitude climates. We know that low-latitude regions have much less variability in day-to-day temperatures when compared with the mid-latitudes, which means the signal of climate change emerges quite quickly, and because of this the frequency of extreme hot days increases rapidly too.”
Majuro, capital of the Marshall Islands, is an atoll in the Pacific Ocean. It is home to about 30,000 people.
Credit: Christopher Michel/flickr
The findings also call into question the commitments made at the landmark Paris conference on climate change last December, at which nations agreed to limit global temperature rises to no more than 2°C, a threshold which scientists regard as the limit of safety, beyond which the ravages of climate change are likely to become catastrophic and irreversible.
However a 2°C rise on average globally could still leave tens or hundreds of millions of people vulnerable to dramatic rises in their regional temperatures, which could make their current way of living impossible to maintain.
Governments are meeting this week in Bonn, the first meeting since the Paris agreement was signed.
Reprinted with permission from The Guardian.
‘99 Percent Chance’ 2016 Will Be Hottest Year
Odds are increasing that 2016 will be the hottest year on the books, as April continued a remarkable streak of record-warm months.
Last month was rated as the warmest April on record by both NASA and the National Oceanic and Atmospheric Administration, which released their data this week. In the temperature annals kept by NOAA, it marked the 12th record warmest month in a row.
How global temperatures have differed from average so far this year.
Click image to enlarge. Credit: NOAA
Global temperatures have been hovering around 1.5°C (2.7°F) above pre-industrial averages — a threshold that’s being considered by international negotiators as a new goal for limiting warming.
While an exceptionally strong El Niño has provided a boost to temperatures in recent months, the primary driver has been the heat that has built up from decades of unabated greenhouse gas emissions.
NOAA announced its temperature data for April on Wednesday, with the month measuring 1.98°F (1.1°C) above the 20th century average of 56.7°F (13.7°C). It was warmer than the previous record-hot April of 2010 by 0.5°F (0.3°C).
NASA’s data showed the month was about the same amount above the average from 1951-1980. The two agencies use different baselines and process the global temperature data slightly differently, leading to potential differences in the exact temperatures anomalies for each month and year.
Both agencies’ records show that global temperatures have come down slightly from the peaks they hit in February and March, which ranked as the most anomalously warm months by NASA and NOAA, respectively.
Climate Central has reanalyzed the temperature data from recent months, averaging the NASA and NOAA numbers and comparing it to the average from 1881-1910 to show how much temperatures have risen from a period closer to preindustrial times.
The analysis shows that the year-to-date temperature through April is 1.45°C above the average from that period. Governments have agreed to limit warming this century to less than 2°C from pre-industrial times and are exploring setting an even more ambitious goal of 1.5°C, which temperatures are currently close to.
“The fact that we are beginning to cross key thresholds at the monthly timescale is indeed an indication of how close we are getting to permanently exceeding those thresholds,” Michael Mann, a climate scientist at Penn State, said in an email.
A year-to-date look at 2016 global temperatures compared to recent years.
Click image to enlarge.
It will take a significant effort to further limit emissions of carbon dioxide and other heat-trapping gases to realize those goals, experts say. Carbon dioxide levels at the Mauna Loa observatory in Hawaii are already poised to stay above 400 parts per million year-round. They have risen from a pre-industrial level of 280 ppm and from 315 ppm just since the mid-20th century.
As El Niño continues to rapidly decay, monthly temperature anomalies are slowly declining. They are still considerably higher than they were just last year, the current title-holder for the hottest year on record.
Given the head start this year has over last, there is a more than 99 percent chance that 2016 will best 2015 as the hottest year on the books, according to Gavin Schmidt, head of NASA’s Goddard Institute for Space Studies, which keeps the agencies temperature data.
If 2016 does set the mark, it will be the third record-setting year in a row.
It is likely, though, that the streak would end with this year, as a La Niña event is looking increasingly likely to follow El Niño, and it tends to have a cooling effect on global temperatures.
But even La Niña years today are warmer than El Niño years of previous decades — a clear sign of how much human caused-warming has increased global temperatures. In fact, the planet hasn’t seen a record cold year since 1911.
Power Plant Emissions Fall to Lowest Level in Decades
Carbon dioxide emissions from electric power plants have fallen to their lowest level in decades, and that trend could help states meet their emissions goals under the Obama administration’s Clean Power Plan if it survives court challenges, according to new U.S. Energy Information Administration data and a New York University analysis.
Carbon dioxide emissions from generating electricity in 2015 were 21 percent below 2005 levels in the U.S. The goal of the Clean Power Plan is to cut emissions by 32 percent below 2005 levels by 2030, mainly from coal-fired power plants.
In raw numbers, generating electricity in the U.S. was the source of 1.9 billion metric tons of carbon dioxide emissions in 2015 — roughly the same as in 1993. Emissions peaked in 2007, when the country’s power plants emitted 2.4 billion metric tons of carbon dioxide. By 2014, power plant emissions had dropped to about 2.05 billion metric tons.
Coal use is the largest single contributor to emissions causing climate change. The Clean Power Plan, which the U.S. Supreme Court has put on hold while legal challenges have their day in court, was critical to establishing U.S. credibility during the Paris climate talks last year. States have until September 2018 to decide how to cut emissions under the plan.
The electric power sector’s carbon emissions are falling for several reasons. Warmer winters in the U.S., influenced by global warming, have reduced the need for people to heat their homes, driving down electric power demand in the winter months, according to the EIA.
There is also a basic shift in how electricity is generated — from coal to natural gas and renewables, EIA analyst Channele Wirman said.
Low natural gas prices have encouraged utilities to shutter coal-fired power plants and build new ones that run on natural gas, which emit roughly half the carbon dioxide as those that use coal. Wind, solar and other renewables helped to cut emissions even more. A decade ago, 8 percent of U.S. electricity came from renewables. Last year, they were the source of 13 percent of the country’s electricity.
A power plant in New York City.
All of that adds up to two things: cleaner air and more climate-friendly electricity.
“Even without the Clean Power Plan in effect, market factors like the low price of natural gas and the declining cost of renewable generation technologies are pushing states toward a cleaner energy mix,” Jack Lienke, senior attorney at NYU’s Institute for Policy Integrity, said.
For example, natural gas is expected to overtake coal this year as the nation’s chief source of electricity, a tax credit is expected to fuel widespread wind and solar power expansion over the next decade and the declining economics of coal are spurring a move toward cleaner energy, according to the institute’s analysis.
The trend toward low-carbon electricity means that states will have a leg up in meeting the Clean Power Plan’s goals even if the plan itself is delayed by the courts.
But there is no guarantee the economics pointing to long-term growth in clean energy will be continue for a long time, and the if the Clean Power Plan survives court challenges, it will help provide certainty for electric power companies if the economic winds change quickly, Lienke said.
“That certainty is helpful to companies and states making long-term investments in clean energy, and it’s helpful to the U.S. in international climate negotiations,” he said.
Marine Parks Help Global Fish Stocks Withstand Warming
New and expanded marine parks and fishing rules could be powerful antidotes for threats of famine as fisheries dwindle from climate change and overfishing, new research has shown.
An ambitious new analysis of big marine data produced from thousands of dives by citizen scientists worldwide has detected a powerful link between the biodiversity of a coral or rocky reef and the size of the fisheries it supports.
Fishing restrictions can help fisheries cope with climate change, new research shows.
Credit: Thangaraj Kumaravel/Flickr
“Biodiversity — the number of species and how different they are — is as important as climate to global production of fish,” said Emmett Duffy, a Smithsonian Institution scientist who led the analysis, published Monday in Proceedings of the National Academy of Sciences. “This was a big surprise."
Previous research has linked climate change with biodiversity declines in the oceans. The new findings show that means warming could also reduce fish stocks, which have been falling as fishermen reach deeper into the oceans for their hauls.
The findings come as the U.S. and other countries create new marine parks to protect ocean biodiversity, and as the world strives through a new United Nations treaty to stem runaway climate pollution. Most of the extra heat from global warming ends up in the oceans.
The U.N. says the world’s fishing fleets are either fully exploiting or already overexploiting 80 percent of monitored fish stocks.
Duffy and four other researchers compared the estimated weights of fish stocks in reefs around the world with a long list of environmental factors, such as nearby human population size, sea-surface temperatures, temperature variability and nutrient pollution. The data came from the global Reef Life Survey project.
Coral and rocky reefs are of special interest to marine ecologists because they serve as nurseries for fish stocks. Research published earlier this year showed Great Barrier Reef coral recover from storms, predators and bleaching more quickly in areas where fishing is banned, helping to restore the natural habitat that’s relied upon by fisheries.
The strongest relationships the scientists discovered in these reef ecosystems were between fish stocks and biodiversity and temperature.
“This suggest that changes in biodiversity are likely to be on a similar scale in terms of their impacts as climate change,” Duffy said. “Biodiversity seems to protect fish communities against climate change.”
The findings add urgency to efforts underway through the United Nations to protect at least 10 percent of the global ocean from fishing and other industrial activities by 2020. So far, less than half that amount has been protected.
Meanwhile, U.N. negotiations began this year in an attempt to regulate fishing on the high seas for the first time. The high seas lie outside of national territories, where fisheries can be legally plundered because domestic laws do not apply. They cover about half of the planet.
Catherine Kilduff, a former marine scientist who now works as an attorney for the nonprofit Center for Biological Diversity, said the new findings are “scientific evidence that we need biodiversity” — not just to benefit wildlife, but to protect fisheries that humans depend upon.
Reef Life Survey diver surveying fish in the Coral Sea.
Credit: Graham Edgar
“The key finding is that biodiversity is the cornerstone of ocean health — and that rings really true for me,” Kilduff said. “We need to do everything we can to promote biodiversity, and the question is how to do that.”
The study was the latest piece of evidence from big-data crunching in support of ecologists’ long-held theory that biodiversity protections are key to supporting large and healthy fisheries. That theory has underpinned efforts to expand ocean protections.
“What’s been done in the past were fairly small scale experiments,” said Andrew Brooks, a University of California, Santa Barbara scientist who researches marine fish populations. “There’s alway uncertainty as to whether it really scales up. What we’re really doing now, which has only been possible in the recent past, is we’re gathering up data.”
Brooks contributed to a study published in 2011 that reached similar conclusions regarding the relationship between biodiversity and fisheries size, and to another study that hasn’t yet been published.
“All three papers are generally in agreement that in areas with higher biodiversity, you tend to see higher levels of biomass,” Brooks said.
Brooks said that once biodiversity has been lost from an ocean, it’s very difficult to replace, suggesting it would be more efficient to protect the ecosystems that foster fish stocks now than try to restore them later.
“Increasing biodiversity is hard,” Brooks said. “It’s all about preventing the loss of biodiversity.”
Sea Level Rise Could Help Marshes Ease Flooding
Along the mid-Atlantic coast, where waters are rising quickly, marshes are on the march, consuming forestland, farms and yards. “Habitats are changing fast here,” said Matt Whitbeck, a biologist at the Blackwater National Wildlife Refuge in Maryland, where dead trees still jut from young marshes.
Newly published modeling shows that a looming acceleration in sea level rise could further accelerate the spread of marshes worldwide.
A ghost forest in Bass River, N.J., where marshland is replacing forestland.
Credit: Ken Able/Rutgers University
Coastal planners value marshes for their ability to hold back floods. When conditions are right, they cling to shifting coastlines like protective scabs, growing taller as tides get higher, slowing waves, erosion and floods.
“For a moderate acceleration in sea-level rise, the marshes could actually get bigger, because they’re going to migrate into uplands at a faster rate,” said Matt Kirwan, a Virginia Institute of Marine Science researcher who led the study, published in Geophysical Research Letters.
“That’s completely different than how we normally think of sea-level rise,” Kirwan said. “We normally think of sea level rise as a threat to marshes.”
Ghost forests of dead trees are already prominent at East Coast sites like Blackwater, which is home to bald eagles and wetland species, and where several thousand acres of forest has died since the 1930s and given way to marshland. The eerie ecosystems are particularly common in New Jersey.
Following a half foot rise last century, heat-trapping pollution is now causing seas to rise more than an inch per decade. That rate is poised to continue increasing. Anywhere between two and six feet of sea level rise is possible this century. The severity of future flooding will depend partly on whether a new United Nations climate treaty succeeds in abruptly slowing warming from fuel burning, deforestation and meat production.
Kirwan studies marshes and he wanted to know more about how the acceleration of sea level rise would affect them. He worked with colleagues to develop models that investigated how marsh erosion, soil accumulation and upland marsh expansion are affected by sea level rise and local topography.
The findings added to evidence that marshes can offer economical solutions to flooding in the backcountry as sea levels change — and that those solutions become expensive near cities.
The researchers reported in their paper that marsh loss is “nearly inevitable” where human structures or steep hills block the upland migration of the marsh ecosystem. But where there are no such barriers, increases in marsh expansion upland are “much more sensitive” to a quickening of sea level rise than rates of marsh loss at the water’s edge.
The modeling showed that marshes can drown once sea level rise reaches rapid rates — rates that are unlikely to be experienced in the near future. Their expansion also depends on sufficient mud swirling in the water, which helps them accumulate soil needed to grow vertically as seas rise.
Sea-level rise has been particularly rapid in the mid-Atlantic, where Kirwan is based, with human and natural forces combining to raise high tide marks at least half a foot from 2002 to 2014. High tide flooding is becoming routine in Annapolis and in other cities along the Eastern seaboard, heralding a looming global crisis.
“What drove our research were all these observations of dead trees along the edges of marshes up and down the Atlantic coast,” Kirwan said. As salty waters rise, shoreline trees die and marsh plants colonize soggy land between the trunks. Mud, branches and muck combine into rich wetland soil, fostering plants and wildlife. “It’s clear that the marsh is migrating upslope.”
Wetland restoration projects are starting to become popular around the world. San Francisco Bay Area voters are considering introducing a parcel tax to help fund marsh restorations. A recent worldwide study showed it’s two to five times cheaper to grow a marsh to shield against the eroding power of waves than to build a barrier from rocks or concrete. Marshes also support fisheries.
EPA surveys have shown just half of America’s remaining wetlands are in good condition. Kirwan’s modeling suggests that providing ample space near a tattered marsh may be the best way to breathe back life into it.
“Our models indicate that management efforts don’t have to focus on preserving the marsh that’s already there,” Kirwan said. “Instead, they should consider where the marshes are going to be in the future.”
In areas where land is expensive, already built over or protected by seawalls, that could be prohibitively expensive, causing city marshes to drown as seas rise.
“An important precondition is that there is a gently sloping transition to natural uplands — and no man-made barriers,” Stijn Temmerman, a University Antwerp professor who studies ecosystem management.
When seawalls, houses and roads stand in the way of marshes’ natural inland migrations, the marshes can disappear. Temmerman says that’s a major threat in Europe, “where there’s a long tradition of building sea walls behind marshes.”
Some American coastal neighborhoods could adapt to regular flooding, such as with elevated buildings or floodable ground floors. But many view the ongoing abandonment of targeted waterfront neighborhoods as inevitable. The new findings show successful coastal retreat may also require abandoning land that’s set back from a waterfront, allowing marshes to migrate into it.
High costs of land, however, mean it’s “very unlikely that land will be made available for wetland migration” along populous stretches of coastline, according to Kristina Hill, an urban ecology and design researcher at the University of California, Berkeley.
“I think wetland migration by natural processes will certainly occur, but mostly in rural or abandoned suburban areas,” Hill said. “The trick will be removing underground and surface systems that will interfere with wetland migration, like underground pipes, contaminated soils, basement foundations and roadways.”
Even in lightly populated areas, American coastlines tend to run parallel with train tracks and highways. They can block the migration of a marsh, and, politically, they can be “almost impossible to relocate,” Hill said. “They’ll form hard edges for wetland migration unless they’re elevated on causeways.”
Despite the prominence of ghost forests on the East Coast, marsh migration is a global phenomenon. Richard Stumpf, a NOAA scientist, documented a spectacular marsh migration nearly 1,000 miles from Blackwater. He worked with the U.S. Geological Survey to analyze landscape changes in the little-populated areas of the eastern Gulf of Mexico.
About 10,000 acres of marshes eroded away or drowned along a section of Florida coastline during 120 years, the scientists reported earlier this year in the journal Estuaries and Coasts. Meanwhile, twice that acreage of forest died and turned into marshland, with further conversions underway.
“We have an understanding that marsh migration can be as important as marsh erosion,” Stumpf said. “This paper is a good example of developing a model to test our understanding.”
Back at Blackwater, Whitbeck and his colleagues have been trying to protect new marshlands from invasive grasses and from marsh-destroying invasive rodents called nutria. Even as they do that, they’re trying to clear a path for future marsh expansion as seas continue to rise — something that’s easier to do in a wildlife refuge than in an urban setting.
“We’re protecting lands within these marsh migration corridors so we can have places for the marshes to migrate into the future,” Whitbeck said. “It’s a very proactive approach.”
CO2 Nears Peak: Are We Permanently Above 400 PPM?
Just three years ago this month, the carbon dioxide monitoring station atop Hawaii’s Mauna Loa reached a significant milestone: the first measurement of CO2 concentrations that exceeded the benchmark of 400 parts per million (ppm). Now, they may never again dip below it.
As CO2 levels once again approach their annual apex, they have reached astonishing heights. Concentrations in recent weeks have edged close to 410 ppm, thanks in part to a push from an exceptionally strong El Niño.
Click image to enlarge.
But it is the emissions from human activities that are by far the main driver of the inexorable climb of CO2 concentrations in the atmosphere. That trend, in turn, is driving the steady rise of global temperatures, which have set record after record in recent months.
Those CO2 levels will soon begin to drop toward their annual minimum as spring triggers the collective inhale of trees and other plant life. But because of the remarkable heights reached this year, the fall minimum, unlike recent years, may not dip below the 400-ppm mark at Mauna Loa.
“I think we’re essentially over for good,” Ralph Keeling, the director of the Mauna Loa CO2 program at the Scripps Institution of Oceanography, said.
And before too long, that will be the case the world over.
Atmospheric carbon dioxide levels are monitored at stations around the world, providing records of the mark humans are leaving on the planet. Keeling’s father, Charles Keeling, began the recordings at Mauna Loa in 1958, revealing not only the annual wiggles created by the seasonal growth and death of vegetation, but the steady rise in CO2 from year to year.
The resulting graph, dubbed the Keeling Curve in his honor, became an icon of climate science.
Click image to enlarge.
Back then, CO2 levels were around 315 ppm (already an increase from preindustrial levels of about 280 ppm), but they have grown steadily, first crossing the 400 ppm threshold in May 2013. The following year saw the first month with an average over that level. Last year, it was three months.
But in each of those years, concentrations dipped back below that level in the fall, but for a shorter and shorter length of time.
While the world’s plants need CO2 to function, they can only soak up so much, leaving behind an excess every year — an excess that slowly lifts both the annual maximum and minimum, just as a rising tide lifts all ships.
That yearly excess (recently about 2 ppm) traps ever more heat in the Earth’s atmosphere, which has raised global temperatures by 1.6°F (0.9°C) since the beginning of the 20th century. In recent months, those temperatures have neared 1.5°C (2.7°F) above those of the late 19th century — a milestone international negotiators are working to potentially avoid. Depending on how much emissions are reduced in the coming decades, the Earth could see another 3°F to 9°F (1.7°C to 5°C) of warming by the end of the century.
El Niño’s Boost
Last year, CO2 hit a weekly peak of about 404 ppm. If the trend had continued as normal, it likely would have been another couple years before year-round levels at Mauna Loa permanently rose above 400 ppm. But then came one of the strongest El Niños on record.
El Niño tends to lead to drought in the tropical regions of the planet, which can mean more wildfires and higher CO2 emissions. This El Niño helped cause a huge leap in CO2 levels compared to last year; over 2015, CO2 concentrations grew by 3.05 ppm, the largest jump on record.
It also marked the fourth consecutive year with a growth rate higher than 2 ppm — another hallmark of global warming is that the annual growth rate of CO2 is accelerating. At the beginning of the Keeling Curve record, the growth rate was only about 0.75 ppm.
Currently, CO2 levels are about 4 ppm higher than this point last year, thanks in part to a particularly big jump in April. Keeling isn’t sure what the exact cause of that jump was, but said it was likely a high-CO2 air mass moving in from Southeast Asia.
Because of that jump, the highest weekly value recorded this year has been 408.6, in mid-April. Daily values reached even higher, closing in on 410 ppm.
Such April jumps are fairly typical, Keeling said, though May generally has a higher monthly average than April because it is more consistently high. (The peak in CO2 levels is also shifting earlier in May because of the longer growing season ushered in by higher global temperatures.)
Permanently Over 400 ppm?
As May turns to June, CO2 levels will come down from their fever pitch, and the question is: How low will they go? Will they dip below 400 ppm one more time, or are we now in an over-400 ppm world.
For his part, Keeling thinks the latter situation is the more likely.
“I think it’s pretty unlikely that Mauna Loa will dip below 400 ppm in the monthly or weekly” averages, he said. That is a sentiment he first expressed in a blog post back in October, when it was becoming clear how strong El Niño would be.
Pieter Tans, lead scientist of NOAA’s Global Greenhouse Gas Reference Network, was more circumspect, saying it depends on how long the current 4-ppm rise from last year lasts into the summer.
Mauna Loa isn’t the only spot poised to move permanently above 400 ppm, though. The Cape Grim station in remote northwestern Tasmania saw its first measurements above 400 ppm on May 10. Now that it has reached that level, it will not dip below again, the scientists who maintain the site told the Sydney Morning Herald.
This is particularly significant because Cape Grim had yet to reach that mark, in part because the Southern Hemisphere has a less pronounced seasonal cycle than the Northern Hemisphere because the Northern Hemisphere has more landmass and plant life. The majority of carbon dioxide emissions also come from the Northern Hemisphere and take about a year to spread across the equator.
Keeling saw this process in action during an airborne mission run by the National Center for Atmospheric Research that measured CO2 levels throughout the depth of the Southern Hemisphere atmosphere in February. The measurements taken during that mission showed that even in some of the remotest reaches of the planet, near Antarctica, air masses had CO2 concentrations over 400 ppm. And those that didn’t were just barely under.
What this means is that “this is the last we'll see of sub-400 ppm CO2 in the Southern Hemisphere, unless we’re able to someday achieve negative emissions,” NCAR scientist Britton Stephens, co-lead principal investigator for the mission, said in a statement.
Keeling suspects that the only places on the globe that may see levels dip below 400 ppm this summer will be at the highest latitudes (which have higher seasonal swings). They could perhaps do so again next summer, but then the planet as a whole will be above 400 ppm for the foreseeable future.
And while that benchmark is somewhat symbolic — the excess heat trapped by 400 ppm versus 399 is small — it serves as an important psychological milestone, Keeling said, a way to mark just how much humans have emitted into the atmosphere.
And with levels this year already nearing 410 ppm, “you realize how fast this is all going,” he said.
Keeling is hopeful, though, that with the signing of the Paris agreement and signs of action to limit emissions by various national governments, the iconic rise of the Keeling Curve will start to plateau.
“If Paris is successful, this curve will look very different in a matter of five or 10 years because it will start to change,” he said “And I hope we see that.”
Editor's note: This story was updated to reflect the confirmation that the Cape Grim CO2 station had made its first measurement over 400 ppm.