Climate 411

Hurricane Harvey: Climate change, staggering costs, and people at the heart of it all

Texans are no stranger to the devastation of hurricanes. I still vividly remember, as a young child in Austin, being scared of Alicia in 1983 – and thankful that we lived at the top of the hill. Alicia caused nearly $2 billion in damages, a record at the time, and the category 3 storm was so destructive that its name was retired. But only a few years later, that record was broken in Texas by Tropical Storm Allison in 2001 ($5 billion), Hurricane Rita in 2005 ($24 billion), and Hurricane Ike in 2008 ($35 billion).

In fact, of the top ten costliest hurricanes of all time in the U.S., nine have been since 2004, and half have been in the past five years. Houston alone has endured three 500-year floods in the past three years. Each of these storms was devastating in its own right, but Harvey brought destruction to a new level.

As a native Texan, this is not the normal I knew. And for those outside Texas, think of the magnitude: You could fit the cities of Boston, Chicago, Manhattan, San Francisco, Santa Barbara, and Washington, D.C. into the geographical area of Houston. So how does Hurricane Harvey fit into the new normal? Here are three things we know for certain.

  1. Climate change increased the intensity and likelihood of the storm

2017 was a devastating year of natural disasters, by any measure, from wildfires in several western states to intense heatwaves in the Southwest to Harvey, followed closely by Hurricanes Irma and Maria. Thanks to the improvement in climate models, scientists are now better equipped to attribute climate change effects to individual natural disasters.

A recent study by hurricane experts in the Proceedings of National Academy of Sciences found that Harvey’s unprecedented 51 inches of rainfall in the Houston area, as well as wind speeds in other parts of the state, were three times more likely and 15 percent more intense than without climate change. The study even called the rainfall “biblical” – as in, it has likely occurred only once since the time the Old Testament was written.

In Texas now, the odds of another Harvey-like rainfall could be nearly 1 in 5 per year by 2100 – put another way, rain of this magnitude could hit the state 18 times more often by the end of the century. Storms that have more than 20 inches of rain in Texas are about six times more likely now than they were at the end of the 20th century, just 18 years ago.

Climate change did not cause Hurricane Harvey, but it certainly made its impact much worse. Like an athlete on steroids, climate change enhances the performance of an already powerful force.

  1. The costs are and will continue to be enormous

According to the National Oceanic and Atmospheric Association (NOAA), the costs from all the 2017 natural disasters clock in at $306 billion – and Harvey comes out on top at $125 billion. Not only is that figure staggering on its face, but if the political leadership continues to go forward as business as usual, the costs of inaction will dwarf these.

Furthermore, these official numbers do not include things like economic impacts in the community, health costs from air and water pollution, mental health costs from the trauma of natural disasters, and repeatedly continuing to rebuild.

Beyond what’s traditionally reported – mainly about homes and businesses – a lot of sectors of the economy were affected by Harvey, such as:

  • Agriculture: Texas A&M University estimates crop and livestock losses at $200 million, with cotton and livestock representing $193 million of that. With Texas leading the nation in cattle and cotton production, those are serious numbers.
  • Fishing: While Gulf oysters took a hit from Harvey, the economic impacts to the fishing communities, especially many immigrant and immigrant-descendant families, along the coast will be felt for a long time. In addition to gear and infrastructure losses, the long-term effects on the marine ecosystem are still unknown. In particular, since oysters filter a lot of water, the loss of oyster populations may have an effect on the bays’ overall health.
  • Oil and gas: 20 percent of offshore oil and gas production was shut down.

If we do not act to mitigate further damage, while adapting our infrastructure and our systems to the reality of climate change, we will face dire financial consequences that may prove impossible to work around.

  1. The impact on people is much deeper than numbers and dollars

Climate change isn't just about studies and storm patterns, it means people are devastated. Some staggering stats from Harvey:

And for many, climate change will increasingly mean moving, not just rebuilding. Some towns and communities along the coast that have fewer resources than big cities like Houston, such as Rockport and Port Aransas, may never fully recover.

Plus, Houston’s no-zoning policy means a lot of pollution and petrochemical hazards are concentrated in one part of the city, which is largely populated by people of color or people with low incomes. Harvey unleashed a toxic stew in these neighborhoods and the communities, which already have fewer resources for rebuilding, may be permanently displaced. Storms don’t discriminate – some of the wealthiest areas in Houston were flooded – but climate change will hit vulnerable communities the hardest.

No time to lose

As Harris County Judge Ed Emmett put it, “Three 500-year floods in three years means either we’re free and clear for the next 1,500 years or something has seriously changed.” Unfortunately, the reality is the latter.

We have the data. We know the stats. There is no excuse to not act on climate change. The leadership of Texas and the U.S. have a duty to protect the citizens and property of this state and country. Ignoring the new normal is reckless.

Photo source: U.S. Army

This post first appeared on EDF's Texas Clean Air Matters blog.

Also posted in Extreme Weather, Greenhouse Gas Emissions / Leave a comment

Natural disasters are no longer purely natural

You may have heard the alarming news that weather and climate disasters in the U.S. killed 362 people in 2017 and caused a record $306 billion in damages.

But also alarming is the fact that many news outlets are still referring to these events as “natural disasters.”

Southeast Texas after Hurricane Harvey – a not-purely-natural disaster. Photo: U.S. Department of Defense

With recent advances in science, researchers have found that human-caused climate change plays a major role in making certain events occur and/or making them worse. That means that many “natural disasters” are no longer purely “natural.”

Here is a look at some not-so-natural disasters:

  • Hurricane Harvey 2017: human-caused climate change made record rainfall over Houston around three times more likely and 15 percent more intense
  • European Extreme Heat 2017: human-caused climate change made intensity and frequency of such extreme heat at least 10 times as likely in Portugal and Spain
  • Australian Extreme Heat 2017: maximum summer temperatures like those seen during 2016-2017 are now at least 10 times more likely with human-caused climate change
  • Louisiana Downpours 2016: human-caused climate change made events like this 40 percent more likely and increased rainfall intensity by around 10 percent
  • European Rainstorms 2016: human-caused climate change made probability of three-day extreme rainfall this season at least 40 percent more likely in France
  • UK Storm Desmond 2015: human-caused climate change made extreme regional rainfall roughly 60 percent more likely
  • Argentinian Heat Wave 2013/2014: human-caused climate change made the event around five times more likely

By employing the term “natural disasters,” news outlets and others are inadvertently implying that all of these events are just misfortunate incidences – rather than consequences of our actions.

This seemingly innocuous phrase supports the idea that dangerous weather is out of our control.

But, we do have some control over their frequency and intensity, and that control is through our emissions of heat-trapping gases.

We need to act on climate, and we need to do it now. Pointing out that we worsen and may even cause these weather disasters may help convince people to do what needs to be done.

Also posted in Basic Science of Global Warming, Extreme Weather, News, Setting the Facts Straight / Read 1 Response

A look back at 2017: The year in weather disasters – and the connection to climate change

Port Arthur, Texas after Hurricane Harvey. Photo: SC-HART

From hurricanes to heat waves, 2017 produced countless headlines concerning extreme weather and the devastation left in its wake.

We tend to think of extreme weather as an unpredictable, external source of destruction. When faced with catastrophes, we don’t always recognize the role we play in intensifying their impacts.

But as human-induced climate change continues to progress, extreme weather is becoming more frequent and dangerous. Without immediate greenhouse gas mitigation efforts, last year’s unprecedented disasters may soon become the norm.

Here’s a look back at the worst weather of 2017 and how these events may have been affected by climate change (and scroll down to see a timeline of the year’s worst weather).

JANUARY

  1. Massive flooding drowns California – Intense rains in January provided a much needed respite from California’s longstanding drought, but quickly tipped from satiating to inundating. Within the first 11 days of the year, California received 25 percent of the state’s average annual rainfall. Flooding and mudslides forced more than 200,000 people to evacuate their homes and caused an estimated $1.5 billion in property and infrastructure damages.

    The rapid shift from drought to flooding may be a marker of climate change. As temperatures warm, precipitation falling as rain rather than snow and expedited snow melt lead to the earlier filling of reservoirs. Such a shift increases the likelihood of both summer droughts and winter flooding, with the latter intensified by a warming atmosphere that holds more moisture and deposits greater precipitation in heavy rainfall events.

  2. Heat wave sizzles in Australia – High heat persisting overnight in the New South Wales and Southern Queensland regions of Australia induced a series of devastating heat waves throughout January and February. Following a record-setting month in which the city reached its highest ever overnight minimum temperature for December, Sydney experienced the hottest night in January since weather records began in the mid-1800s.

    Analysis has shown that these extreme summer temperatures are 10 times as likely due to the influence of climate change. With rising global temperatures, heat waves are expected to become more intense, frequent, and longer lasting. Australia was just one of many regions to experience these developing changes in 2017.

  3. Extreme heat melts the North Pole – Recent history of escalating temperatures in the Arctic could not dull the shock when temperatures near the North Pole reached more than 50 degrees Fahrenheit above regional averages this winter. The heat wave associated with this spike is not only dramatic in intensity, but frequency – heat this extreme usually occurs about once each decade, yet this event was the third recorded in just over a month.

    There exists an essential feedback between sea ice melt and Arctic warming – the more we warm, the more ice melts, lowering the region’s reflectivity of sunlight and increasing warming intensity. While these processes are usually gradual, weather variability can kick dramatic warming events into high gear. The winter heat waves experienced in the Arctic provide examples of such a combination, which may occur every few years should we reach a 2 degree Celsius global temperature rise.

FEBRUARY

  1. Drought brings risk of famine to Somalia – At a time when a staggering 6.2 million people – half of Somalia’s population – required urgent humanitarian aid, the World Health Organization released an official warning that Somalia was on the verge of famine. Such categorization would clock in as Somalia’s third famine in 25 years, the most recent of which led to the death of 260,000 people.

    After years of scarce rainfall, the nation continues to face widespread food insecurity, reduced access to clean water, and increased risk for drought-related illness. Analysis of both observational and modeling data suggests that only a small increase in the nation’s dry extremes can be attributed to climate change. However, as dry regions become progressively drier in a warming climate, similar national disasters may become increasingly common.

JUNE

  1. Extreme heat blisters the Southwestern United States – In June, an intense heat wave blazed across the Southwestern U.S. and left record high temperatures in its trail. Daily records included 127 degrees Fahrenheit in Death Valley. All-time records were reached in Las Vegas, Nevada and Needles, California at 117 degrees Fahrenheit and 125 degrees Fahrenheit, respectively. High heat triggered public health concerns and led to power outages in the California Central Valley, the buckling of highways in West Sacramento, and the cancelation of 50 flights out of Phoenix Sky Harbor Airport for American Airlines alone.

    While high temperatures are typical of the low-humidity pre-monsoon season in the Southwest, the unprecedented magnitude of these numbers and the shift towards an earlier extreme heat season may be a signal of the changing climate.

Greenland's wildfires, as seen from space. Photo: NASA

JULY

  1. Once-icy Greenland engulfed in flames – In historically icy Greenland, wildfires have typically been of minimal concern. As a result, when the largest wildfire in the country’s history broke out at the end of July, there existed virtually no framework to assess the event’s health and infrastructure risk.

    As global temperatures rise and Greenland’s ice melts, the once barren landscape can fill with vegetation and expand the likelihood of forest fire outbreak. Climate change simultaneously lengthens and intensifies drought in the region, while increasing the likelihood of thunderstorms (a major catalyst of wildfires). Wildfires in turn intensify regional warming, as the fires’ soot deposits black carbon on the pristine snow cover, reducing the region’s reflectivity and accelerating ice sheet melt.

  2. “Lucifer” plagues Europe – Europe’s most sustained extreme heat event since the deadly 2003 heatwave (in which climate change was responsible for half of the 1050 recorded deaths) brought temperatures so reminiscent of the Inferno that locals named the event “Lucifer.” As temperatures throughout the region surpassed 104 degrees Fahrenheit, two deaths were recorded and a 15 percent increase in hospital emergency emissions was observed in Italy. The heatwave also caused pollution levels to soar and spurred wildfires throughout Portugal, just a few months after fires in Pedrógão Grande killed 60 and injured more than 250.

    Research concerning previous extreme heat in Europe has shown that climate change renders the maximum summer temperatures observed in regions such as Spain 500 times more likely than in the pre-industrial era. As global temperatures continue to rise, extreme heat will only become more familiar.

  3. Southeast Asia inundated by widespread floods – More than 41 million people were affected by massive floods and landslides that rippled through nations including Bangladesh, India, and Nepal. Losses experienced by the region included more than 1,300 lives and the displacement of 600,000. Two simultaneous pressures – the push for urbanization and neglect towards developing sustainable draining systems – renders the region highly vulnerable to these natural disasters.

    The link between the Southeast Asian monsoon season and climate change is complex, dependent upon a variety of entwined weather systems and intricate regional topography. More study is necessary to predict the influence of a changing climate on this monsoon system in order to prepare the region for impact and increase communities’ resilience.

Puerto Rico after Hurricane Irma. Photo: U.S. Customs and Border Protection

AUGUST

  1. Atlantic hurricane season leaves devastation in its wake – Deadly storms Harvey, Irma, Maria, and Ophelia dominated the news in August, killing more than 150 people and causing more than $300 billion in damages in just the United States.

    As the atmosphere holds seven percent more moisture with each one degree Celsius temperature rise, individual tropical storms can now deposit more rainfall. Recent studies have estimated that climate change rendered Harvey’s extreme rainfall three times more likely and 15 percent more intense. 27 trillion gallons of rain fell over Texas and Louisiana from Hurricane Harvey alone, setting the record for the highest tropical cyclone rainfall in the continental US. Sea level rise of 10 to 12 inches in cities such as Miami dramatically increased the destruction caused by the storm surges associated with Hurricane Irma, which were as high as 10 feet. Warming waters driving hurricane development and strength ushered in Hurricane Maria – Puerto Rico’s strongest storm in 85 years – and Hurricane Ophelia, which set records for the farthest east a major hurricane has traveled in the Atlantic and the worst storm in history to make landfall in Ireland.

OCTOBER

  1. Western United States’ forests set ablaze – Wildfires devastated Northern California this October, with more than 245,000 acres burned and 14,000 homes destroyed. Insured losses in the region amounted to more than $3 billion, but danger does not end when the fires are extinguished. The remaining ash and debris (including hazardous waste, electronic waste, and heavy metal contamination) can be spread by wind and rain, posing even further health concerns to those nearby. The increased temperatures and decreased water availability associated with climate change increases the risk of wildfires. Due to recent temperature and dryness extremes in California, even engine heat from parked cars has been cited as the source of major fires.

    The duration of the fire season has also begun to lengthen, as spring and summer temperatures rise and snowmelt begins earlier. California wildfires ignited once again in December outside of Los Angeles, creating even more destruction than those in the north. Covering an area of more than 425 square miles and displacing more than 100,000 people, the Thomas fire ranks as the second largest fire in the state’s history. While dryness and high temperatures triggering the fire’s outbreak are associated with La Niña's current presence in the region, climate change serves to exacerbate both conditions and facilitate the dramatic losses experienced by California residents.

The direct influence of climate change on many of these events suggests that more devastating catastrophes lie ahead. But the future is not written in stone.

Should we recognize the intensification of these extreme weather events, the power to decrease greenhouse gas emissions worldwide and prevent increasingly hostile weather remains in our hands.

Also posted in Arctic & Antarctic, Basic Science of Global Warming, Extreme Weather / Read 2 Responses

Why Honeycutt is such an alarming choice for EPA's science advisory panel

Michael Honeycutt – the man set to lead the U.S. Environmental Protection Agency’s prestigious Science Advisory Board – has spent most of his career as a credentialed counterpoint against almost anything the EPA has proposed to protect human health.

Fortunately, his lone voice for the Texas Commission on Environmental Quality rarely carried beyond the Lone Star State. Until now.

The EPA science advisory panel Honeycutt will chair is supposed to provide the agency with independent scientific expertise on a wide range of issues. In a highly unusual move, EPA Administrator Scott Pruitt picked the Texan for the job even though he has never been a member of the board.

More than Honeycutt’s inexperience, however, what worries me most is his faulty logic and what this means for science at the EPA.

Honeycutt downplays ozone dangers

A toxicologist by training, Honeycutt has criticized the EPA’s health-based standards for ozone because “most people spend more than 90 percent of their time indoors,” reducing their exposure to the ubiquitous pollutant.

Houston residents know differently. The city’s worst day for lung-damaging ozone this year happened while many people were outside for long hours of cleanup after Hurricane Harvey.

Honeycutt doubled-down on his position that ozone is not harmful to human health in a 2014 interview with the Texas Tribune.

“I haven’t seen the data that says lowering ozone will produce a health benefit,” he said. “In fact, I’ve seen data that shows it might have a negative health benefit.”

Honeycutt’s statement suggests he believes that more air pollution might actually be good for you.

…even though ozone can cause premature death

I am a toxicologist in Texas, too, and here is the truth about ozone: The pollutant can exacerbate asthma, lung disease and heart disease – and even lead to premature death.

The current acceptable limit, recommended during the George W. Bush administration and set under Obama’s in 2015, is 70 parts per billion, a standard that the public health community still believes is too high. The EPA’s own science advisors had recommended a limit as stringent as 60 ppb to protect human health.

Honeycutt spent millions to refute science

In his Texas role, Honeycutt responded to the recommendation by paying more than $2.6 million for research that says tighter ozone rules would cost the state billions of dollars annually with little or no impact on public health.

“Every part per billion that they don’t lower it is millions of dollars,” Honeycutt told the Houston Chronicle. “So we think that the return on investment in this is just phenomenal. Just phenomenal.”

And it’s not just ozone that seems to be a target for Honeycutt. He also has issues with protections against mercury, particulate matter and air toxics.

The reality is, however, that by failing to improve air quality, we’re paying more in health and social costs. This is real money lost on hospital visits, and on missed work and school days.

…and now he’ll steer EPA science

All this matters because Honeycutt, as the board’s chair, will help prioritize which issues the EPA decides to investigate and pick the scientists who review studies and reports before they come to the full board.

My worry is that he will continue down a path that is destructive to public health protections, a well-known pattern within the Trump administration.

We know that clean air and a strong economy go hand in hand – and that claims by industry doomsayers claims are unsubstantiated.

But none of that matters to an administration that scrubs qualified scientists from serving on advisory committees, that eradicates scientific data from websites that do not support the its agenda, and that does not want to be challenged.

Honeycutt’s appointment is yet another attack against science. With American health at stake, we can not stay silent about this latest EPA development.

This post originally appeared on our EDF Voices blog.

Image source: Source: Flickr/Science Democrats.

Also posted in Health, Policy / Comments are closed

It’s now, it’s us, it’s not over – the top 7 takeaways from the new climate change report

Earth as seen from a NOAA weather satellite. Photo: NASA

The U.S. government recently released the Climate Science Special Report (CSSR) – the work of fifty climate science experts who compiled and analyzed the latest knowledge about the physical science of climate change from more than 1,500 scientific journal articles and reports.

The CSSR is often referred to as the first volume of the Fourth National Climate Assessment. National Climate Assessments have been Congressionally mandated since 1990 to be prepared every four years. The second and final volume of the Fourth National Climate Assessment will focus on societal impacts and will be released in 2018.

The CSSR is packed with valuable and scientifically robust information – but it’s almost 600 pages long. If you don’t have time to read it all, don’t worry. We quote some of the most important, and most alarming, facts below.

Here are some of the major takeaways of the CSSR:

It’s now

  • Global average temperature since 1900 is the warmest in the history of modern civilization. Global annually averaged surface air temperature has increased by about 1.8 degrees Fahrenheit (1.0 degrees Celsius) over the last 115 years (1901 to 2016).
  • Sea level rise is accelerating and has already impacted dozens of U.S. cities. Globally averaged sea level has risen by about 7 to 8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993. The incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities.
  • Several extreme weather and climate events are increasing in intensity and frequency across the U.S. and the world. Heavy rainfall is increasing in intensity and frequency, heatwaves have become more frequent in the United States since the 1960s, and the incidence of large forest fires in the western United States and Alaska has increased since the early 1980s. However, extreme cold temperatures and cold waves are less frequent.
  • Earlier spring melt and reduced snowpack are affecting water resources in the western U.S.

It’s us

  • There is no convincing alternative explanation supported by observational evidence that warming over the last century is caused by anything other than human activities. 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.

It’s not over

  • Without major reductions in emissions, annual average global temperature relative to preindustrial times could increase by 9 degrees Fahrenheit (5 degrees Celsius) or more by the end of this century. With significant reductions in emissions, the increase in annual average global temperature could be limited to 3.6 degrees Fahrenheit (2 degrees Celsius) or less.
  • With further warming comes further sea level rise. Global average sea levels are expected to continue to rise — by at least several inches in the next 15 years and by one to four feet by 2100. A rise of as much as eight feet by 2100 cannot be ruled out. Sea level rise will be higher than the global average on the East and Gulf Coasts of the United States.

The CSSR should put any doubts about whether climate change is a serious threat to rest. The report makes it crystal clear that it is – and that we need to act before it gets worse.

Also posted in Basic Science of Global Warming, Extreme Weather / Comments are closed

Everything you need to know about climate tipping points

(This post was co-authored by EDF Climate Scientist Ilissa Ocko)

Imagine cutting down a tree. Initially, you chop and chop … but not much seems to change. Then suddenly, one stroke of the hatchet frees the trunk from its base and the once distant leaves come crashing down.

It’s an apt metaphor for one of the most alarming aspects of climate change – the existence of “tipping elements.”

These elements are components of the climate that may pass a critical threshold, or “tipping point,” after which a tiny change can completely alter the state of the system. Moving past tipping points may incite catastrophes ranging from widespread drought to overwhelming sea level rise.

Which elements’ critical thresholds should we worry about passing thanks to human-induced climate change?

You can see the answer on this graphic – and find more information below.

The most immediate and most worrisome threats

  • Disappearance of Arctic Summer Sea Ice – As the Arctic warms, sea ice melts and exposes dark ocean waters that reflect sunlight much less efficiently. This decreased reflectivity causes a reinforcement of Arctic warming, meaning that the transition to a sea-ice free state can occur on the rapid scale of a few decades. Some scientists have suggested that we have already passed this tipping point, predicting that Arctic summers will be ice-free before mid-century.
  • Melting of the Greenland Ice SheetThe Arctic warming feedback described above may one day render Greenland ice-free. Research predicts that the tipping point for complete melt can occur at a global temperature rise of less than two degrees Celsius – a threshold that may be surpassed by the end of this century. While the full transition to an ice-free Greenland will take at least a few hundred years, its impacts include global sea level rise of up to 20 feet.
  • Disintegration of the West Antarctic Ice Sheet – The bottom of this ice sheet lies beneath sea level, allowing warming ocean waters to slowly eat away at the ice. There is evidence that this tipping point has already been surpassed – possibly as early as 2014. Like the Greenland Ice Sheet, full collapse would require multiple centuries, but it could result in sea level rise of up to 16 feet.
  • Collapse of Coral ReefsHealthy corals maintain a symbiotic relationship with the algae that provide their primary food source. As oceans warm and become more acidic, these algae are expelled from the corals in an often fatal process called coral bleaching. Research predicts that most of our remaining coral systems will collapse even before a global temperature rise of two degrees Celsius.

Tipping points in the distant future

  • Disruption of Ocean Circulation Patterns – The Thermohaline Circulation is driven by heavy saltwater sinking in the North Atlantic, but this water is becoming fresher and lighter as glaciers melt in a warming climate. The change in water density may prevent sinking and result in a permanent shutdown of the circulation. Research suggests that weakening of the Thermohaline Circulation is already in progress, but that an abrupt shutdown is unlikely to occur in this century. Some models suggest that these changes may prompt a secondary tipping element in which the subpolar gyre currently located in the Labrador Sea shuts off. Such a change would dramatically increase sea level, especially on the eastern coast of the United States.
  • Release of Marine Methane HydratesLarge reservoirs of methane located on the ocean floor are stable thanks to their current high pressure-low temperature environment. Warming ocean temperatures threaten the stability of these greenhouse gas reservoirs, but the necessary heat transfer would require at least a thousand years to reach sufficient depth, and may be further delayed by developing sea level rise.
  • Ocean AnoxiaIf enough phosphorous is released into the oceans – from sources including fertilizers and warming-induced weathering, or the breakdown of rocks –regions of the ocean could become depleted in oxygen. However, this process could require thousands of years to develop.

Potentially disastrous elements, but with considerable uncertainty

  • Dieback of the Amazon Rainforest Deforestation, lengthening of the dry season, and increased summer temperatures each place stress on rainfall in the Amazon. Should predictions that at least half of the Amazon Rainforest convert to savannah and grasslands materialize, a considerable loss in biodiversity could result. However, the dieback of the Amazon Rainforest ultimately depends on regional land-use management, and on how El Niño will influence future precipitation patterns.
  • Dieback of Boreal Forests – Increased water and heat stress could also lead to a decrease in boreal forest cover by up to half of its current size. Dieback of boreal forests would involve a gradual conversion to open woodlands or grasslands, but complex interactions between tree physiology, permafrost melt, and forest fires renders the likelihood of dieback uncertain.
  • Weakening of the Marine Carbon Pump – One mechanism through which oceanic carbon sequestration takes place is the marine carbon pump, which describes organisms’ consumption of carbon dioxide through biological processes such as photosynthesis or shell building. As ocean temperatures rise, acidification progresses, and oxygen continues to be depleted, these natural systems could be threatened and render the carbon sequestration process less efficient. More research is necessary in order to quantify the timescale and magnitude of these effects.

Tipping elements complicated by competing factors

  • Greening of the Sahara/Sahel As sea surface temperatures rise in the Northern Hemisphere, rainfall is projected to increase over the Sahara and Sahel. This increased rainfall would serve to expand grassland cover in the region, but is balanced by the cooling effect of human-emitted aerosols in the atmosphere.
  • Chaotic Indian Summer MonsoonThe fate of the Indian Summer Monsoon similarly depends upon a balance of greenhouse gas warming and aerosol cooling, which strengthen and weaken the monsoon, respectively. On the timescale of a year, there is potential for the monsoon to adopt dramatic active and weak phases, the latter resulting in extensive drought.

More research necessary to establish as tipping elements

  • Collapse of Deep Antarctic Ocean CirculationAs in the case of the Thermohaline Circulation, freshening of surface waters in the Southern Ocean due to ice melt may slowly alter deep water convection patterns. However, the gradual warming of the deep ocean encourages this convection to continue.
  • Appearance of Arctic Ozone HoleUnique clouds that form only in extremely cold conditions currently hover over Antarctica, serving as a surface for certain chemical reactions and facilitating the existence of the ozone hole. As climate change continues to cool the stratosphere, these “ice clouds” could begin formation in the Arctic and allow the development of an Arctic ozone hole within a year.
  • Aridification of Southwest North America As global temperatures rise, consequential changes in humidity prompt the expansion of subtropical dry zones and reductions in regional runoff. Models predict that Southwest North America will be particularly affected, as moisture shifts away from the southwest and into the upper Great Plains.
  • Slowdown of the Jet Stream A narrow and fast moving air current called a jet stream flows across the mid-latitudes of the northern hemisphere. This current separates cold Arctic air from the warmer air of the south and consequentially influences weather in its formation of high and low pressure systems. A slowing of the jet stream has been observed over recent years. Should slowing intensify, weather patterns could persist over several weeks with the potential to develop into extended extreme weather conditions.
  • Melting of the Himalayan Glaciers – Several warming feedbacks render the Himalayan glaciers vulnerable to dramatic melt within this century, though limitations on data availability complicate further study. Dust accumulation on the mountainous glaciers and the continual melt of snow and ice within the region both prompt a decrease in sunlight reflectivity and amplify regional warming.

Gradual, continuous changes

  • More Permanent El Nino State90 percent of the extra heat trapped on Earth’s surface by greenhouse gases is absorbed by the oceans. Though still under debate, the most likely consequence of this oceanic heat uptake is a gradual transition to more intense and permanent El Nino/Southern Oscillation (ENSO) conditions, with implications including extensive drought throughout Southeast Asia and beyond.
  • Permafrost MeltingAs global temperatures rise and the high latitudes experience amplified warming, melting permafrost gradually releases carbon dioxide and methane into the atmosphere and creates a feedback for even more warming.
  • Tundra Transition to Boreal Forest – Much like the conversion of the Amazon Rainforest and boreal forests to other biomes, tundra environments may transition into forests as temperatures increase. However, this process is more long-term and continuous.

With a range of critical thresholds on the horizon, each tipping element demonstrates the potential implications of allowing climate change to progress unchecked.

As tipping points loom ever closer, the urgency for emissions mitigation escalates in hopes of sustaining the Earth as we know it.

Also posted in Arctic & Antarctic, Basic Science of Global Warming, Extreme Weather, Oceans / Comments are closed