Selected category: Oceans

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, Science| Comments are closed

A real Halloween horror story: the five scariest aspects of climate change

Halloween has arrived, and it’s time once again for goblins, gremlins, and ghost stories.

But there’s another threat brewing that’s much more frightening – because it’s real.

An unrecognizable world is quickly creeping up on us as climate change progresses – and the anticipated impacts are enough to rattle anyone’s skeleton.

Here are five of the scariest aspects of climate change. Read on if you dare ….

  1. Extreme weather is becoming more extreme

A changing climate paves the way for extreme weather events to live up to their name.

In 2017 alone we saw fatal events worldwide, including:

The fingerprints of climate change can be found on each of these events.

As global temperatures continue to rise, heat waves are expected to become more intense, frequent, and longer lasting.

Scientists also predict that rainfall patterns will continue to shift, increasing regional risk for widespread drought and flooding.

Montana, 2002. Photo: U.S. Forest Service

Drought conditions may also prompt wildfires to occur more frequently and within a longer fire season. The wildfire season in the western U.S. is already weeks longer than in previous years.

Hurricanes are also influenced by climate change. Rising sea surface temperatures, a moister atmosphere, and changing atmospheric circulation patterns have the potential to increase hurricanes’ power and travel paths.

Extreme weather intensification impacts human health and development in many ways – extreme heat events directly generate health hazards such as heat stroke, while drought and wildfires threaten crop and ecosystem stability.

The 2017 hurricane season has already demonstrated the shocking consequences of intensified hurricanes and flooding, with Hurricanes Harvey, Irma, and Maria killing more than 150 people and causing as much as $300 billion in damages in the U.S. alone.

  1. Tipping points loom in near future

A particularly alarming facet of climate change is the threat of irreversible changes to climate conditions, called “tipping elements.”

These components of the climate system earn their title from a possession of critical thresholds, or “tipping points,” beyond which a tiny change can dramatically alter the state of the system.

Many tipping elements have been identified by scientists, and some may have already passed their critical threshold. For example, a vicious cycle of sea ice melt has already been triggered, leading scientists to predict that Arctic summers will be ice-free before mid-century.

Imminent tipping points also exist for melting ice sheets, particularly those of Greenland and West Antarctica, where full ice sheet collapse could result in global sea level rise of up to 20 feet and 16 feet respectively.

Coral reefs too are rapidly approaching a grave tipping point. Essential relationships between algae and corals begin to break down as ocean waters rise in temperature and acidity. Without stabilizing these changes, the majority of global reef systems may collapse before global temperatures reach a two-degree Celsuis warming threshold.

  1. Coastal communities battle sea level rise

Sea level rise is one of the most visible impacts of climate change, as increased coastal erosion physically erases continental borders.

As the climate warms, ocean waters expand and ice sheets and glaciers melt. Both factors contribute to a rising sea level at an accelerating rate. Communities in Alaska and several Pacific Islands are already fleeing rising seas – relocating as their villages are engulfed and eroded.

Rising sea levels also intensify damages from extreme weather events such as hurricanes. A higher sea level allows storm surges to grow in height and volume, exacerbating flooding and associated damages.

As water levels continue to rise, more coastal communities will feel the consequences. Many major cities are located on coastlines, with almost 40 percent of U.S. citizens living in coastal cities.

Protecting people from this creeping threat will be difficult and costly – as we’ve already seen in the aftermath of coastal storms such as Superstorm Sandy.

  1. Humans are nearing uncharted climate territory

A globally averaged two-degree Celsius (or 3.6 degrees Fahrenheit) of warming over preindustrial levels is the most widely suggested threshold we need to stay “well” below.

The threshold was first proposed by William Nordhaus in the 1970’s, in part because of its historical significance – the human species has never lived during a time in which global temperatures were equivalent to two-degrees Celsius above preindustrial levels.

The unprecedented nature of this benchmark provided a foundation for alarm that carried the two-degrees Celsius value into political and scientific discussions for decades.

In a changing climate, unprecedented events will become the norm.

In some cases, they already have.

As infectious diseases spread to previously untouched regions and an Arctic ozone hole threatens to open, people are beginning to catch the first glimpses of the new world we are creating – one that is in many ways more hostile and dangerous than the one we leave behind.

  1. Many American politicians deny the problem

Perhaps the only thing more terrifying than the impacts of climate change is the overwhelming denial of their existence by some political leaders in the U.S.

The Paris Agreement served as a major step forward in promoting climate change mitigation policy on an international scale, with almost every nation agreeing to tackle this looming threat.

Then in June, President Trump announced his intent to withdraw from the agreement. That means the United States will be one of only two countries – out of almost 200 – failing to participate in the accords.

The same efforts towards dismantling U.S. climate progress can be seen in recent national policy. Environmental Protection Agency Administrator Scott Pruitt (who recently claimed that carbon dioxide is not a major contributor to global warming) is perhaps the most visible of an exhausting list of leaders within the current Administration who deny climate science. The Administration is trying to undermine or reverse policies addressing climate change, including the Clean Power Plan, and information about climate change is vanishing from official agency websites.

The rest of the globe is striving to implement meaningful climate policy, including China’s unparalleled growth in renewable energy support. Soon the U.S. will be left in the dust in the race for a greener world.

Be afraid. Be very afraid. Then do something about it.

We can’t protect you from the monsters hiding under your bed. But combating the ominous impacts of climate change is a much more hopeful endeavor.

For more information on how you can help, click here.

 

Also posted in Arctic & Antarctic, Basic Science of Global Warming, Extreme Weather, International, News, Policy, Science| Read 2 Responses

Hurricane Matthew And Climate Change: What We Know So Far

Image source: NASA

Hurricane Matthew. Image source: NASA

As I write this, Hurricane Matthew is battering the Atlantic coast of Florida, having wreaked havoc on Haiti and the Bahamas. In Haiti hundreds lost their lives due to the Hurricane’s destructive winds and storm surge.

With half a million Floridians already without power even before Matthew makes landfall, there is sure to be significant damage in Florida and other portions of the southeast U.S. from this Category 3 storm, the first major hurricane to strike the U.S. since Wilma in 2005. Our first and highest priority is to help the victims and others in the path of the storm.

However, as with any destructive weather event, people are asking about the role of climate change.

We know that increases in sea level caused by climate change result in higher and more destructive storm surges, like the one that swamped lower Manhattan during Superstorm Sandy in 2012. Coastal towns suffer greater damage because the ocean starts out higher, and the storm shoves more water inland. Coastal states like South Carolina and Florida – and the rest of us through taxes and insurance rates – will pay billions as a result.

But what about the connection between climate change and the strength of hurricanes themselves?

Hurricanes are fueled by the warm waters of the tropical oceans, which have been warming as the result of increased emissions of greenhouse gases.

However, hurricanes are also impacted by wind shear – the change of wind speed and direction with height. For a hurricane to grow and strengthen it needs a low wind shear environment, and some research indicates that climate change may actually increase wind shear over the tropical Atlantic. And that’s the rub. When it comes to climate change and hurricanes, the warming oceans and increasing wind shear are in competition. Science is still working out which mechanism will dominate as the global climate continues to warm – so stay tuned.

But there is more to the story than just the relationship between the intensity or frequency of hurricane and global warming. Because the climate system is so complex, no storm happens in a vacuum. Scientists have been working on the issue of “attribution”— How much can we know about the link between specific storms and climate change? The organization Climate Central has also been working intensively in this area.

While we await attribution studies, we shouldn’t lose site of the bigger picture: we already know that climate change is doing tremendous damage to our environment and our economy. Citibank estimates the cost of inaction on climate change is in the trillions. So let’s first help those hurt by this storm, then focus on cutting the pollution that is causing so much damage to our world.

Also posted in Basic Science of Global Warming, Extreme Weather, Greenhouse Gas Emissions, Science| Comments are closed

Six Climate Tipping Points: How Worried Should We Be?

One of the biggest fears about climate change is that it may be triggering events that would dramatically alter Earth as we know it.

Known to scientists as “tipping events,” they could contribute to mass extinction of species, dramatic sea level rise, extensive droughts and the transformation of forests into vast grasslands – among other upheavals our stressed world can ill afford.

Here are the top six climate events scientists worry about today.

1. The Arctic sea ice melts

The melting of the Arctic summer ice is considered to be the single greatest threat, and some scientists think we’ve already passed the tipping point.

As sea ice melts and the Arctic warms, dark ocean water is exposed that absorbs more sunlight, thus reinforcing the warming. The transition to an ice-free Arctic summer can occur rapidly – within decades – and this has geopolitical implications, in addition to a whole ecosystem being disrupted.

Photo: Smudge 900)

2. Greenland becomes ice-free

The warming of the Arctic may also render Greenland largely ice-free. While Greenland’s ice loss will likely reach the point of no return within this century, the full transition will take at least a few hundred years.

The impacts of the Greenland ice melt is expected to raise sea levels by up to 20 feet.

Half of the 10 largest cities in the world, including New York City, and one-third of the world’s 30 largest cities are already threatened by this sea level rise. Today, they are home to nearly 1.8 billion people.

Other vulnerable American cities include Miami, Norfolk and Boston.

Photo: siralbertus

3. The West Antarctic ice sheet disintegrates

On the other side of Earth, the West Antarctic ice sheet is also disintegrating. Because the bottom of this glacier is grounded below sea level, it’s vulnerable to rapid break-up, thinning and retreat as warm ocean waters eat away at the ice.

Scientists expect the West Antarctic ice sheet to “tip” this century, and there is evidence that it already began happening in 2014.

However, the entire collapse of the glacier, which would raise sea level by 16 feet, could take a few hundred years.

Photo: BBC World Service

4. El Niño becomes a more permanent climate fixture

The oceans absorb about 90 percent of the extra heat that is being trapped in the Earth system by greenhouse gases. This could affect the ocean dynamics that control El Niño events.

While there are several theories about what could happen in the future, the most likely consequence of ocean heat uptake is that El Niño, a natural climate phenomenon, could become a more permanent part of our climate system.

That would cause extensive drought conditions in Southeast Asia and elsewhere, while some drought-prone areas such as California would get relief.

The transition is expected to be gradual and take around a century to occur – but it could also be triggered sooner.

Photo: Austin Yoder

 5. The Amazon rain forest dies back

Rainfall in the Amazon is threatened by deforestation, a longer dry season, and rising summer temperatures.

At least half of the Amazon rainforest could turn into savannah and grassland, which – once triggered – could happen over just a few decades. This would make it very difficult for the rainforest to reestablish itself and lead to a considerable loss in biodiversity.

However, the reduction of the Amazon ultimately depends on what happens with El Niño, along with future land-use changes from human activities.

Photo: World Bank

 6. Boreal forests are cut in half

Increased water and heat stress are taking a toll on the large forests in Canada, Russia and other parts of the uppermost Northern Hemisphere. So are forest disease and fires.

This could lead to a 50-percent reduction of the boreal forests, and mean they may never be able to recover. Instead, the forest would gradually transition into open woodlands or grasslands over several decades.

This would have a huge impact on the world’s carbon balance because forests can absorb much more carbon than grasslands do. As the forest diminishes, the climate will be affected as will the Earth’s energy balance.

However, the complex interaction between tree physiology, permafrost and fires makes the situation tricky to understand.

Photo: Gord McKenna

Other concerns…

As if that’s not enough, there are a few other tipping events that scientists are also concerned about, but they are even more complex and harder to predict. Examples of such events include the greening of the Sahara and Sahel, the development of an Arctic ozone hole and a chaotic Indian summer monsoon.

How do we keep from tipping over?

We know from measurements that the Earth has had many climate-related tipping events throughout its history. Today’s situation is different, because humans are now driving these changes and the warming is occurring at a faster rate.

But as humans we also have the power to change the trajectory we’re on – possibly in a matter of a few years. We think we know how.

Also posted in Arctic & Antarctic, Basic Science of Global Warming, Extreme Weather, Greenhouse Gas Emissions, Plants & Animals| Read 1 Response

New report: How climate change is impacting where you live

The National Climate Assessment (NCA) report, prepared by the U.S. Global Change Research Program, is essentially the U.S. equivalent of the Intergovernmental Panel on Climate Change (IPCC): Using the best available science, over 300 experts synthesized current understanding of observed and future climate changes and impacts, particularly in the U.S. The third ever NCA was released today, and concludes beyond a reasonable scientific doubt that Americans are being affected by climate change.

Among the findings:

  • U.S. average temperatures have increased by 1.3 to 1.9ºF since record-keeping began in 1895, and most of this warming has occurred since 1970
  • Heavy precipitation has increased in many parts of the country
  • Extremes such as heat waves, droughts, floods, and North Atlantic hurricanes are more frequent and/or intense
  • Summer sea ice in the Arctic has halved since record-keeping began in 1979
  • Sea level rise has increased coastal erosion and storm surge damage

These changing conditions produce a variety of tangible stresses on society by affecting human health, water resources, agriculture, energy, infrastructure, and natural ecosystems. The particular impacts vary by region, but no corner of the country is immune to the change.

So what’s happening where you live?

Source: National Climate Assessment

Unless we take immediate action to curb our emissions of heat-trapping gases, the foreseeable future will be plagued by further warming and worsening impacts. The good news is that because we know what the cause is, we also know what is needed in order to stabilize our planet. We must come together now—locally, nationally, and internationally—and work towards a better future.

This post first appeared on our EDF Voices blog

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

Antarctica's Glacial Melt

There should no longer be any doubt. Climate change is here, and it is happening. 26,000 broken heat records this summer speak for themselves.

Extreme weather events hit home. Another consequence of climate change, by contrast – rising sea levels – often seems far away and far off.

“Far away” is easily dismissed. U.S. coasts are as much in danger as sea shores anywhere else on the planet.

"Far off” often seems tougher to address. After all, seas have only risen by inches so far. Projections say we could see three or more feet by the end of the century.

Even right now, though, we’re seeing the evidence of sea level rise. Antarctic ice sheets have been melting to the tune of 24 cubic miles of melt water per year, every year, since 2002.

That is a huge number, but a fairly abstract number. So The Globalist designed a quiz to make the giant quantity feel a bit more real. EDF was honored to help with the research for the quiz.

See if you can answer the question:

If you were to take the melt-off from Antarctica's ice sheets over the past decade (2002 to 2012) and pour it into a California-sized Jell-O mold, how high would the water rise?

The right answer might surprise you. Hint: Think Paul Sturgess, the world's tallest professional basketball player.

And check out The Globalist quiz for more details.

Also posted in Arctic & Antarctic, Extreme Weather, News, Science| Read 1 Response
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