Patching up the ozone hole: The success of the Montreal Protocol

New model results show that the Antarctic ozone hole would have grown in size by 40% by 2013 if ozone depleting chemicals had not been banned in the 1980s.

CGS researchers at the University of Leeds’ School of Earth and Environment used computer models to determine the impacts of ozone damaging substances (ODSs) on the Earth’s ozone layer. They show that international efforts to control the release of ODSs has had a significant and measurable impact on reducing the size of the hole in the ozone layer.

The results from the study are published in Nature Communications.

Arctic ozone without the Montreal Protocol (left) and following its implementation (right).

The Montreal Protocol is regarded as one of the most important global treaties in history. The protocol was signed in 1987 with the aim to control the international use of ozone damaging substances. Without it, the researchers reveal that not only would the ozone hole over Antarctic be much bigger now but there would also be a significant hole over the Arctic region. The Arctic hole would have been large enough to affect much of northern Europe, including the UK. This ozone loss would have led to increases in surface ultraviolet radiation of up to 14% in the United Kingdom with a consequent increase in skin cancer and other related skin illnesses.

The new research simulated what the ozone hole would have been like today if nothing had been done. Lead researcher, Professor Martyn Chipperfield told the BBC: ”We would be living in an era of having regular Arctic ozone holes.”

Background

The ozone layer is a region of the Earth’s atmosphere that absorbs most of the sun’s harmful ultraviolet radiation. It contains higher amounts of ozone (O₃) compared other parts of the atmosphere, hence the name.

False-color view of total ozone over the Antarctic pole on 23rd May 2015. The purple and blue colours are where there is the least ozone, and the yellows and reds are where there is more ozone.
Source: NASA

In the late 1970s scientists began to notice large holes appearing within the ozone layer over the Antarctic. The discovery of the annual depletion of ozone above the Antarctic was first announced by scientists at the British Antarctic Survey, in a paper which appeared in Nature, 1985. The cause of the depletion was linked to the use of chlorine, bromine and other chemical gases reaching the atmosphere. These were thought to be released from the extensive use of chlorofluorocarbons (CFCs) in business and industry during the 60s and 70s.

The discovery of the Antarctic ozone hole helped stimulate the signing in 1987 of the Montreal Protocol, an international treaty to limit production of chlorine-and bromine-containing ozone depleting substances.

The study concludes that, since the signing and enforcement of the Montreal Protocol levels of chlorine and bromine containing ozone depleting chemicals in the atmosphere have peaked and then declined. And this has resulted in a steady recovery of the holes in the ozone layer over the past two decades.

More information:

[1] Quantifying the ozone and ultraviolet benefits already achieved by the Montreal Protocol, Nature 2015
[2] CGS and Leeds researchers involved in the study:
– Professor Martyn Chipperfield
– Dr Sandip Dhomse
[3] http://www.nature.com/nature/journal/v315/n6016/abs/315207a0.html
[4] http://ozone.unep.org/new_site/en/montreal_protocol.php
[5] Regular NASA images of the Antarctic ozone hole: http://ozonewatch.gsfc.nasa.gov/

Amazon rainforest trees “living faster and dying younger” while absorbing less carbon

The most extensive land-based study of the Amazon to date reveals it is losing its capacity to absorb carbon from the atmosphere. From a peak of two billion tonnes of carbon dioxide each year in the 1990s, the net uptake by the forest has halved and is now for the first time being overtaken by fossil fuel emissions in Latin America.

The results of this monumental 30-year survey of the South American rainforest, which involved an international team of almost 100 researchers and led by the University of Leeds, were published last month in the journal Nature.

Measuring Amazon trees, Peru. Credit: Roel Brienen

Over recent decades the remaining Amazon forest has acted as a vast ‘carbon sink’ – absorbing more carbon from the atmosphere than it releases – helping to put a brake on the rate of climate change. But this new analysis of forest dynamics shows a huge surge in the rate of trees dying across the Amazon.

Lead author Dr Roel Brienen, from the School of Geography at the University of Leeds, said: “Tree mortality rates have increased by more than a third since the mid-1980s, and this is affecting the Amazon’s capacity to store carbon.”

Initially, an increase in carbon dioxide in the atmosphere – a key ingredient for photosynthesis – led to a growth spurt for the Amazon’s trees, the researchers say. But the extra carbon appears to have had unexpected consequences.

Study co-author Professor Oliver Phillips, also from the University’s School of Geography, said: “With time, the growth stimulation feeds through the system, causing trees to live faster, and so die younger.”

Recent droughts and unusually high temperatures in the Amazon may also be playing a role. Although the study finds that tree mortality increases began well before an intense drought in 2005, it also shows that drought has killed millions of additional trees.

RAINFOR team monitoring the Amazon canopy, Peru. Credit: Kuo-Jung Chao

Dr Brienen said: “Regardless of the causes behind the increase in tree mortality, this study shows that predictions of a continuing increase of carbon storage in tropical forests may be too optimistic.

“Climate change models that include vegetation responses assume that as long as carbon dioxide levels keep increasing, then the Amazon will continue to accumulate carbon. Our study shows that this may not be the case and that tree mortality processes are critical in this system.”

The study involved almost 100 scientists, many working for decades across eight countries in South America. The work was coordinated by RAINFOR, a unique research network dedicated to monitoring the Amazonian forests.

To calculate changes in carbon storage they examined 321 forest plots across the Amazon’s six million square kilometres, identified and measured 200,000 trees, and recorded tree deaths as well as growth and new trees since the 1980s.

“All across the world even intact forests are changing”, added Professor Phillips. “Forests are doing us a huge favour, but we can’t rely on them to solve the carbon problem. Instead, deeper cuts in emissions will be required to stabilise our climate.”

Videos: http://www.rainfor.org/en/videos

A map of the plots in the Amazon where tree measurements were taken for the study. Credit: Georgia Pickavance, RAINFOR / GLC2

More information:
[1] The RAINFOR project website: http://www.rainfor.org/en

A melting Arctic and weird weather: the plot thickens

By Jennifer Francis, Rutgers University

Everyone loves to talk about the weather, and this winter Mother Nature has served up a feast to chew on. Few parts of the US have been spared her wrath.

Severe drought and abnormally warm conditions continue in the west, with the first-ever rain-free January in San Francisco; bitter cold hangs tough over the upper Midwest and Northeast; and New England is being buried by a seemingly endless string of snowy nor’easters.

Yes, droughts, cold and snowstorms have happened before, but the persistence of this pattern over North America is starting to raise eyebrows. Is climate change at work here?

Wavier jet stream

One thing we do know is that the polar jet stream – a fast river of wind up where jets fly that circumnavigates the northern hemisphere – has been doing some odd things in recent years.

Rather than circling in a relatively straight path, the jet stream has meandered more in north-south waves. In the west, it’s been bulging northward, arguably since December 2013 – a pattern dubbed the “Ridiculously Resilient Ridge” by meteorologists. In the east, we’ve seen its southern-dipping counterpart, which I call the “Terribly Tenacious Trough.” (See picture, below.)

Source: NOAA

These long-lived shifts from the polar jet stream’s typical pattern have been responsible for some wicked weather this winter, with cold Arctic winds blasting everywhere from the Windy City to the Big Apple for weeks at a time.

We know that climate change is increasing the odds of extreme weather such as heatwaves, droughts and unusually heavy precipitation events, but is it making these sticky jet-stream patterns more likely, too? Maybe.

Slowing, drunken path

The jet stream is a dastardly complex creature, and figuring out what makes it tick has challenged atmospheric scientists since it was discovered about 75 years ago. Even more elusive is figuring out how climate change will affect it.

Jet streams exist because of differences in air temperature. In the case of the polar jet stream, which is responsible for most of the weather we experience around the middle-latitudes of the northern hemisphere, it’s the cold Arctic butting against warmer areas to the south that drives it. (A more in-depth explanation can be found here.) Anything that affects that temperature difference will affect the jet stream.

This is where climate change comes in: the Arctic is warming much faster than elsewhere. That Arctic/mid-latitude temperature difference, consequently, is getting smaller. And the smaller differential in temperatures is causing the west-to-east winds in the jet to weaken.

Strong jets tend to blow straight west to east; weaker jets tend to wander more in a drunken north/south path, increasing the likelihood of wavy patterns like the one we’ve seen almost non-stop since last winter.

When the jet stream’s waves grow larger, they tend to move eastward more slowly, which means the weather they generate also moves more slowly, creating more persistent weather patterns.

NASA/Goddard Space Flight Center Scientific Visualization Studio

At least, that’s the theory. Proving it is not easy because other changes are happening in the climate system simultaneously. Some are natural fluctuations, such as El Niño, and others are related to increasing greenhouse gases.

We do know, however, that the Arctic is changing in a wholesale way and at a pace that makes even Arctic scientists queasy. Take sea ice, for example. In only 30 years, its volume has declined by about 60%, which is causing ripple effects throughout the ocean, atmosphere, and ecosystem, both within the Arctic and beyond. I’ve been studying the Arctic atmosphere and sea ice my entire career and I never imagined I’d see the region change so much and so fast.

‘Stuck’ weather patterns

To study the effects of Arctic change on weather patterns, we have good measurements of atmospheric temperatures and winds going back to the late 1970s, when satellites started providing data, and pretty good measurements back to the late 1940s.

My colleagues and I have been using this information to measure the waviness of the jet stream and whether it is behaving differently since the Arctic started its rapid warm-up about 20 years ago. Because the upper atmosphere is such a cacophony of swirling winds, however, measuring changes in the jet stream’s waviness is tricky, as it’s not a metric that scientists have traditionally used.

Our challenge, then, is to find new methods to measure waviness and determine whether any changes we find are related to rapid Arctic warming, to some other change in the climate system, or to just random chance. While the story is still in early days, the plot is thickening.

Several groups around the globe, including my colleagues and me, are trying to understand the linkages between rapid Arctic warming and changes in weather patterns.

A number of recent studies have found what appears to be a solid connection between sea-ice loss in an area north of western Russia during the fall and a rash of abnormally cold winters in central Asia. The loss of sea ice favors a northward bulge in the jet stream, which strengthens surface high pressure to the east. That shift pumps cold Arctic air southward into central Asia.

Other studies suggest that Arctic warming in summer leads to a split jet stream – or two separated rivers of wind – which tends to trap the waves. Those stationary waves cause weather conditions to remain “stuck” for long periods, increasing the likelihood of extreme heat waves, droughts and flooding events in Eurasia and North America.

Our own new work, published last month in Environmental Research Letters, uses a variety of new metrics to show that the jet stream is becoming wavier and that rapid Arctic warming is playing a role. If these results are confirmed, then we’ll see our weather patterns become more persistent.

In other words, Ridiculously Resilient Ridges and Terribly Tenacious Troughs may become the norm, along with the weather woes they cause.

This article was originally published on The Conversation.
Read the original article. Feature photo credits:  Stuart Rankin/Flickr, CC BY-NC

The American snow storm

Climate change in 18 tweets!

The latest IPCC report on climate change represents our most up to date understanding of the Earth’s climate, it’s changing behaviour and projections for the future.

CGS scientist Professor Piers Forster, one of the lead authors of the new synthesis report, has summarised the summary in just 18 tweets.

Map of what each country has promised at the climate summit

World leaders gathered yesterday for a crucial United Nations meeting to encourage 120 member states to sign up to a new comprehensive global climate agreement in Paris next year.

The last such meeting in 2009 ended with no concrete results. However the meeting yesterday was hailed by the United Nations Secretary General Ban Ki-moon, saying “never before have so many leaders gathered to commit to action on climate change”.

The interactive map below shows what each country has promised (source: mashable.com).

Note. This is not an exhaustive list of initiatives might be updated.

 

More information:
[1] http://mashable.com/2014/09/23/un-climate-summit-country-promises-map
[2] http://www.un.org/climatechange/summit/
[3] http://www.bbc.co.uk/news/world-29319363

How can we weigh a cloud?

CGS air quality expert Dr Jim McQuaid has been filming a BBC two-part documentary Operation Cloud Lab: Secrets of the Skies. The documentary follows a team of scientists as they explore the earth’s atmosphere, travelling in an airship. The expedition begins with an examination of clouds and how we can determine the weight of an average cloud.You might be surprised at the result!

You can watch the first episode on BBC iplayer.

Ekbal

 

Twin Tornadoes hit Nebraska, United States

Twin tornadoes are an exceptionally rare weather phenomenon. Two large tornadoes hit the town of Pilger in the U.S. state of Nebraska last Monday, 16th June.

The video above shows the two violent tornadoes ripping through the countryside. The BBC reports that at least one person is dead and at least 19 are hurt.

Check out our earlier post for more information on tornadoes, how they form and how their strength is calculated.

Tornadoes: Rotating Destruction

A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a large rain cloud.

Most tornadoes have wind speeds less than 110 miles per hour, are about 76 metres across, and travel several kilometers before losing all its energy and dissipating. However, some extreme tornadoes can attain wind speeds of more than 300 miles per hour, stretch more than two miles across, and stay on the ground for more than 100 km!

These violent weather events can rip paths of destruction through towns and cities and kill large numbers of people.

Tornado Formation
Although, no two tornadoes are the same, they all need certain conditions before they can form – particularly intense heat.

Winds from different directions cause the rising air to rotate.
Source: BBC

• As the ground temperature increases, warm, wet air heats up and starts to rise.
• When this warm, moist, air meets cold dry air, it explodes upwards, puncturing the air layer above. At this stage a thunder cloud may begin to build.
• This develops into a storm – there may be rain, thunder and lightning.
• Winds from different  directions can case the upward moving air to rotate
• This forms the characteristic cone shape we associate with tornadoes.

Tornado Strength Scale
There are several scales for rating the strength of tornadoes. The Enhanced Fujita Scale (EFS) rates tornadoes by the amount of damage caused by the tornado. This is the most common rating scale used by most countries.

The Enhanced Fujita Scale splits tornado strength into six categories.

The Enhanced Fujita Scale for tornadoes

 

Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes occur in the Tornado Alley region of the United States.

Ekbal

More Information:
[1] http://news.bbc.co.uk/1/hi/in_depth/5328524.stm

Half of the United States in the grip of droughts

The central plains and the American Southwest have been experiencing persistent drought conditions for the past several years. However, recent analysis of satellite images acquired by NASA (figure above) show that, as of May 6th 2014, even larger parts of the U.S. are experiencing drought conditions. Nearly 15 percent of the country is in the grip of extreme droughts.

The entire state of California is in some level of drought, with the period between the last twelve months the driest since records began in 1885. The impact of drought on California’s farms, forests, and wild lands has been widespread. At least 54 percent of the nation’s wheat crop is affected by some level of drought, as is 30 percent of corn and 48 percent of cattle.

The financial and sociological burden of the drought on the country as a whole will only increase as drought conditions persist.

Ekbal

More information:
[1] http://earthobservatory.nasa.gov/IOTD/view.php?id=83650&src=fb
[2] http://earthobservatory.nasa.gov/IOTD/view.php?id=83124
[3] http://earthobservatory.nasa.gov/IOTD/view.php?id=79316