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Melting Greenland ice now source of 25% of sea level rise, researchers say

Ocean levels rose 50 percent faster in 2014 than in 1993, with meltwater from the Greenland ice sheet now supplying 25 percent of total sea level increase compared with just 5 percent 20 years earlier, researchers reported Monday.

http://www.japantimes.co.jp/news/2017/06/27/world/science-health-world/melting-greenland-ice-now-source-25-sea-level-rise-researchers-say/#.WVWU6YiGOHs

The findings add to growing concern among scientists that the global watermark is climbing more rapidly than forecast only a few years ago, with potentially devastating consequences.

Hundreds of millions of people around the world live in low-lying deltas that are vulnerable, especially when rising seas are combined with land sinking due to depleted water tables, or a lack of ground-forming silt held back by dams.

Major coastal cities are also threatened, while some small island states are already laying plans for the day their drowning nations will no longer be livable.

“This result is important because the Intergovernmental Panel on Climate Change (IPCC)” — the U.N. science advisory body — “makes a very conservative projection of total sea level rise by the end of the century,” at 60 to 90 cm (24 to 35 inches), said Peter Wadhams, a professor of ocean physics at the University of Oxford who did not take part in the research.

That estimate, he added, assumes that the rate at which ocean levels rise will remain constant.

“Yet there is convincing evidence — including accelerating losses of mass from Greenland and Antarctica — that the rate is actually increasing, and increasing exponentially.”

Greenland alone contains enough frozen water to lift oceans by about 7 meters (23 feet), though experts disagree on the global warming threshold for irreversible melting, and how long that would take once set in motion.

“Most scientists now expect total rise to be well over a meter by the end of the century,” Wadhams said.

The new study, published in Nature Climate Change, reconciles for the first time two distinct measurements of sea level rise.

The first looked one-by-one at three contributions: ocean expansion due to warming, changes in the amount of water stored on land, and loss of land-based ice from glaciers and ice sheets in Greenland and Antarctica.

The second was from satellite altimetry, which gauges heights on the Earth’s surface from space.

The technique measures the time taken by a radar pulse to travel from a satellite antenna to the surface, and then back to a satellite receiver.

Up to now, altimetry data showed little change in sea levels over the last two decades, even if other measurements left little doubt that oceans were measurably deepening.

“We corrected for a small but significant bias in the first decade of the satellite record,” co-author Xuebin Zhang, a professor at Qingdao National Laboratory of Marine Science and Technology in China’s Shandong Province, told AFP.

Overall, the pace of global average sea level rise went up from about 2.2 mm a year in 1993, to 3.3 mm a year two decades later.

In the early 1990s, they found, thermal expansion accounted for fully half of the added millimeters. Two decades later, that figure was only 30 percent.

Andrew Shepherd, director of the Centre for Polar Observation and Modelling at the University of Leeds in England, urged caution in interpreting the results.

“Even with decades of measurements, it is hard to be sure whether there has been a steady acceleration in the rate of global sea level rise during the satellite era because the change is so small,” he said.

Disentangling single sources — such as the massive chunk of ice atop Greenland — is even harder.

But other researchers said the study should sound an alarm.

“This is a major warning about the dangers of a sea level rise that will continue for many centuries, even after global warming is stopped,” said Brian Hoskins, chair of the Grantham Institute at Imperial College London.

New study confirms the oceans are warming rapidly

Although there’s some uncertainty in the distribution among Earth’s ocean basins, there’s no question that the ocean is heating rapidly

As humans put ever more heat-trapping gases into the atmosphere, the Earth heats up. These are the basics of global warming. But where does the heat go? How much extra heat is there? And how accurate are our measurements? These are questions that climate scientists ask. If we can answer these questions, it will better help us prepare for a future with a very different climate. It will also better help us predict what that future climate will be.

The most important measurement of global warming is in the oceans. In fact, “global warming” is really “ocean warming.” If you are going to measure the changing climate of the oceans, you need to have many sensors spread out across the globe that take measurements from the ocean surface to the very depths of the waters. Importantly, you need to have measurements that span decades so a long-term trend can be established.

These difficulties are tackled by oceanographers, and a significant advancement was presented in a paper just published in the journal Climate Dynamics. That paper, which I was fortunate to be involved with, looked at three different ocean temperature measurements made by three different groups. We found that regardless of whose data was used or where the data was gathered, the oceans are warming.

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In the paper, we describe perhaps the three most important factors that affect ocean-temperature accuracy. First, sensors can have biases (they can be “hot” or “cold”), and these biases can change over time. An example of biases was identified in the 1940s. Then, many ocean temperature measurements were made using buckets that gathered water from ships. Sensors put into the buckets would give the water temperature. Then, a new temperature sensing approach started to come online where temperatures were measured using ship hull-based sensors at engine intake ports. It turns out that bucket measurements are slightly cooler than measurements made using hull sensors, which are closer to the engine of the ship.

During World War II, the British Navy cut back on its measurements (using buckets) and the US Navy expanded its measurements (using hull sensors); consequently, a sharp warming in oceans was seen in the data. But this warming was an artifact of the change from buckets to hull sensors. After the war, when the British fleet re-expanded its bucket measurements, the ocean temperatures seemed to fall a bit. Again, this was an artifact from the data collection. Other such biases and artifacts arose throughout the years as oceanographers have updated measurement equipment. If you want the true rate of ocean temperature change, you have to remove these biases.

Another source of uncertainty is related to the fact that we just don’t have sensors at all ocean locations and at all times. Some sensors, which are dropped from cargo ships, are densely located along major shipping routes. Other sensors, dropped from research vessels, are also confined to specific locations across the globe.

Currently, we are heavily using the ARGO fleet, which contains approximately 3800 autonomous devices spread out more or less uniformly across the ocean, but these only entered service in 2005. Prior to that, temperatures measurements were not uniform in the oceans. As a consequence, scientists have to use what is called a “mapping” procedure to interpolate temperatures between temperature measurements. Sort of like filling in the gaps where no data exist. The mapping strategy used by scientists can affect the ocean temperature measurements.

Finally, temperatures are usually referenced to a baseline “climatology.” So, when we say temperatures have increased by 1 degree, it is important to say what the baseline climatology is. Have temperatures increased by 1 degree since the year 1990? Since the year 1970? Since 1900? The choice of baseline climatology really matters.

In the study, we looked at the different ways that three groups make decisions about mapping, bias, and climatology. We not only asked how much the oceans are warming, but how the warming differs for various areas (ocean basins) and various depths. We found that each ocean basin has warmed significantly. Despite this fact, there are some differences amongst the three groups. For instance, in the 300-700 meter oceans depths in the Pacific and Southern oceans, significant differences are exhibited amongst the tree groups. That said, the central fact is that regardless of how you measure, who does the measurements, when or where the measurements are taken, we are warming.

The lead author, Dr. Gonjgie Wang described the importance of the study this way:

Our study confirms again a robust global ocean warming since 1970. However, there is substantial uncertainty in decadal scale ocean heat redistribution, which explains the contradictory results related to the ocean heat changes during the “slowdown” of global warming in recent decade. Therefore, we recommend a comprehensive evaluation in the future for the existing ocean subsurface temperature datasets. Further, an improved ocean observation network is required to monitor the ocean change: extending the observations in the boundary currents systems and deep oceans (below 2000-m) besides maintaining the Argo network.

In plain English, it will be important that we keep high-quality temperature sensors positioned throughout the oceans so in the future we will be able to predict where our climate is headed. We say in science that a measurement not made is a measurement lost forever. And there are no more important measurements than of heating of the oceans.

Exposure to pollution in Hong Kong is worst in the home, study reveals

It’s not just on the city’s streets where we are at risk from dangerous PM2.5 particulates – three-quarters of daily personal exposure is indoors

http://www.scmp.com/news/hong-kong/health-environment/article/2097540/exposure-pollution-hong-kong-worst-home-study

Your home may be your refuge in Hong Kong, but not from air pollution. It’s probably worse.

Exposure to PM2.5 particulates small enough to lodge deep in the lungs and most harmful to human health have been found to be just as high – or higher – inside people’s homes as they are outdoors or during the commute to work on an average weekday.

A two-year study by think tank Civic Exchange and City University, funded by investment bank Morgan Stanley, found that most urban dwellers are exposed to concentrations of PM2.5 during their daily commute that are almost always above average limits set by the World Health Organisation, and generally above readings at the nearest air quality monitoring station.

Breathe easier, Hong Kong is on course to hit global air pollution target

While the Environmental Protection Department’s 16 stations can monitor and assess ambient and roadside air quality across districts, the study fills a relatively wide gap in statistics on individual-level exposure to pollution in different “micro-environments”.

Co-author Dr Zhi Ning reported finding that people were exposed to air pollution risks not just outdoors but also indoors at home or the office.

“Your 24 hours are spent in different environments,” the City University air pollution expert said. “You may think that even if its very polluted outside, you are more safe inside. But it really depends on what that indoor environment is like.”

The researchers employed 73 volunteers who carried lunchbox-sized “personal exposure kits” fitted with sensors and GPS, 24 hours a day for a year around the city.

They found that most spent more than 85 per cent of each weekday indoors, which broke down to 42 per cent of the day at home, 34 per cent in the office, 4 per cent commuting and 11 per cent outdoors or in other indoor areas.

Homes were found to contribute 52 per cent of an individual’s personal exposure to PM2.5 compared with 13 per cent for offices, 4 per cent while commuting, 18 per cent outdoors and 14 per cent in other indoor areas.

The average PM2.5 concentration measured in homes – 42.5 micrograms per cubic metre – was three to four times lower than outdoors but slightly higher than while commuting and three times higher than in the office.

Factors for the PM2.5 build up in homes, Ning surmised, could range from cooking and the type of gas used to proximity to a construction site or smoking tobacco. And this was exacerbated by poor ventilation and dirty air filters. Offices tended to have better ventilation systems. Flats on lower floors were also exposed to more pollution.

But Ning found little correlation between personal exposure and district pollution. A person who spent more time in better ventilated indoor areas in heavily polluted Sham Shui Po, for example, could have a lower exposure to PM2.5 than the station reading and vice versa.

“Right now we only rely on [the department’s] data but they only provide a general, ballpark figure,” Civic Exchange research fellow and co-author Simon Ng Ka-wing said.

“It is important to know how much air pollution we are exposed to on a personal level. This would allow us to make better decisions as to when to go or not to go somewhere.”

The study recommended the government do more to promote better indoor air quality in homes and implement a comprehensive management programme.

A government spokesman said: “The EPD has been conducting promotional and educational activities, including exhibitions and seminars, to promote practices to achieve good indoor air quality.”

Additional reporting by Brian Wong

Trump has reheated debate with US withdrawal from Paris Agreement, former UN climate chief says

Speaking on sidelines of three-day World Sustainable Built Environment Conference in Hong Kong, Christiana Figueres insisted the global shift towards reducing carbon emissions would not be shaken.

The United Nations’ former climate chief has struck a defiant note against US President Donald Trump [1]’s pullout from the landmark Paris accord, insisting the global shift towards reducing carbon emissions will not be shaken.

In an interview with the Post, Christiana Figueres, who formerly headed the UN Framework Convention on Climate Change, even “thanked” Trump for effectively reinvigorating the discussion over global warming and making it headline news again. But she admitted it was sad to see the US give up its leading role.

“The announcement was a political message that Mr Trump wanted to give out, geared toward his political base,” said Figueres, who headed the negotiations leading to the Paris agreement in 2015 [3]

“Most of the US economy, most cities, states and corporations, will continue because they know its in their own interest.”

She was speaking on the sidelines of the three-day World Sustainable Built Environment Conference in Hong Kong on Monday, the city’s largest ever conference on sustainable buildings and urban development. Tackling climate change [4] in the face of rapid urbanisation is the key theme.

Trump’s politically-motivated gesture, Figueres said, would have limited impact on America, given that more than 175 US mayors, a growing number of states and more than 1,000 corporations had pledged to continue upholding commitments to the Paris Agreement.

“It is the White House which stepped out of [Paris], not the US economy,” she said. “That’s actually a sad statement to make as under normal conditions, a president should speak for the economy and the majority.”

Figueres brushed off Trump’s announcement as one riddled with inaccuracies, not least because there was no legal basis for it – no country can withdraw from the accord until three years after ratification – and his claims of bringing back coal industry jobs.

“It is not feasible and Mr Trump knows it,” she said, adding that most coal jobs had already been killed by cheap natural gas as a result of the recent shale revolution, and mining jobs had been taken over by mechanisation and automation.

“It will be increasingly difficult for other heads of state to take Mr Trump seriously,” she added, suggesting that Trump had undermined his country’s credibility.

Figueres said it would be inevitable that China – the world’s biggest carbon emitter – continued the charge as its leaders recognised decarbonisation was “good for their economy”.

Figueres, who now vice-chairs the Covenant of Mayors for Climate and Energy, said built-up environments contributed to one-fifth of global emissions. The conference was being held in Hong Kong as it was a gateway to Asia, she said.

“Asia marks whether the world is going to succeed in climate change actions or not.”

Tobacco To Fossil Fuels: Tracing the Roots of Trump’s Claims on Paris Climate Deal

To understand why President Donald Trump pulled the United States out of the global Paris climate agreement, we might start by looking at the sources he relied on to justify his decision.

https://www.desmogblog.com/2017/06/01/tobacco-fossil-fuels-tracing-roots-trump-s-claims-paris-climate-deal

But we’re not going to start there, but we will end there.

Instead, let’s go back to the early 1990s. The tobacco industry was facing multiple bans on advertising its products in countries around the world.

So the tobacco industry took ownership of a study that reviewed a bunch of other studies about the claimed impacts of tobacco advertising on actual tobacco consumption.

In short, the study, handed to Phillip Morris International, concluded there was no real link between tobacco advertising and smoking levels. Studies that had found a link were probably flawed, the report claimed.

The reports, the letters, and the memos back and forth, are all buried away in the Tobacco Industry Documents Archive at the University of California – San Francisco.

Clearly, the report would help the tobacco industry to argue there was no need to regulate the advertising of its products, because that advertising didn’t make a difference to smoking levels one way or the other.

National Economic Research Associates

The company that carried out that tobacco study was National Economic Research Associates.

Why is this relevant to Donald Trump and his decision to pull out of the Paris climate agreement?

When Trump spoke of the “onerous energy restrictions” he claimed the Paris deal placed on the United States, he cited figures from a report by the very same National Economic Research Associates (NERA).

According to the NERA study, the Paris agreement would cut coal and gas production, and “cost” America 2.7 million jobs.

Fossil Fuel Interests

Two groups, namely the American Council for Capital Formation (ACCF) and the U.S Chamber of Commerce, sponsored the NERA report (incidentally, a New York Times investigation described the chamber as Big Tobacco’s Staunch Friend in Washington, due to its advocacy for the industry).

NERA has also produced reports supporting the LNG industry and the coal industry.

The ACCF has, over the years, accepted funds from a string of major corporations and industry groups, including ExxonMobil, the American Petroleum Institute and foundations linked to the billionaire petrochemical brothers Charles and David Koch.

As a fact check by the Associated Press on the part of Trump’s speech citing the NERA study published points out:

“The study makes worst-case assumptions that may inflate the cost of meeting U.S. targets under the Paris accord while largely ignoring the economic benefits to U.S. businesses from building and operating renewable energy projects.

Academic studies have found that increased environmental regulation doesn’t actually have much impact on employment. Jobs lost at polluting companies tend to be offset by new jobs in green technology.”

A separate team of economists and scientists has also checked the claims made in the NERA report, which has previously been cited by failed Republican Presidential candidate (and climate science denier) Ted Cruz. They come to similarly unflattering conclusions to the AP fact check.

So in the end, we have President Trump relying on a questionable report paid for by groups with a clear vested interest in undermining the Paris agreement.

Cigarette, Anyone?

When reporters were being briefed in the hours before Trump walked out to the White House Rose Garden, it was Trump’s energy aide Mike Catanzaro making the calls.

As DeSmog’s Steve Horn has pointed out, Catanzaro is a former fossil fuel and energy lobbyist with a history of attacking climate science.

He also spent time working with Senator James Inhofe – the Republican who claims global warming is the greatest hoax ever. Catanzaro is just one of a parade of former industry lobbyists now in top positions in the Trump administration.

The Paris climate deal, struck in late 2015, was rightly declared a historic moment.

No doubt too, Trump’s declaration that he will join Nicaragua and Syria outside the deal will also be seen as historic.

It was a decision to delay action to regulate an industry, based on tired old propaganda techniques and the self-serving analysis of a polluting industry under attack.

Cigarette, anyone?

The Guardian view on air pollution: playing politics with the nation’s health

The high court shouldn’t have been asked to decide on this. But it has rightly ruled against the government’s latest efforts to delay action on air quality

https://www.theguardian.com/commentisfree/2017/apr/27/the-guardian-view-on-air-pollution-playing-politics-with-the-nations-health

Thanks to this government’s intransigence about tackling air pollution, the battle to improve the quality of the air we breathe has played out not in the political arena, but in the courts. Time after time, the government has found itself on the wrong side of the law: first for its failure to meet legally binding European targets on harmful nitrogen dioxide emissions; then, for failing to produce an adequate plan to address these. Its latest delaying tactic has been to claim it could not meet this week’s court-imposed deadline for publishing a new draft plan, because of the “purdah” convention ruling out new government announcements in the run-up to an election.

And so it has fallen to judges yet again to take the government to task over its failure to act. Today’s ruling took apart the government’s case: its own purdah guidance sets out exemptions where public health is at risk. As the judge pointed out, why would it be better to have parties debating what ought to be in a draft air pollution plan, when it could be debating what is actually in it?

The government’s real motivations are political, not procedural. Having delayed taking meaningful action for seven years, it is clearly nervous about proposing any measures that hit drivers of diesel cars during an election campaign. Its political cowardice is astounding – and pointless. Public attitudes have shifted in recent years, and London’s Labour mayor, Sadiq Khan, has made tackling air pollution one of his top priorities. The government is unlikely to face opposition to tougher action from any of its mainstream political opponents, and is enjoying double-digit poll leads.

Yet it continues to shirk its responsibilities to the nation’s public health. Today’s air pollution may be less visible than the smogs that settled over our cities in the 1950s, but it is a deadly killer, responsible for upwards of 40,000 premature deaths per year. London breached its annual air pollution limit just five days into 2017, and legal limits were easily surpassed in the vast majority of local authorities. The effects are particularly pernicious for children whose lungs are still developing.

The human cost makes the government’s latest attempts to delay a disgrace. The two-month extension it was seeking for its final plan could have meant thousands of avoidable premature deaths, all in service of not wanting to jeopardise a marginal number of votes in an election that it is on course to win handsomely. It’s a sick calculus.

The good news is that air pollution is easier to tackle than other environmental and public health challenges. Unlike climate change, it is relatively localised: city-scale actions to address pollution levels can have a marked effect on their air quality. Much (though by no means all) of the problem comes down to emissions from diesel vehicles and, to a greater extent than in other areas of public health, consumers are highly responsive to financial incentives. The irony is that we know this because many have switched from petrol to diesel as a result of sweeteners introduced back when diesel was thought to be more environmentally friendly due to its lower carbon emissions.

But heavy lobbying from the car industry in Westminster and Brussels has staved off firm action. European emissions tests for diesel cars have been far easier to manipulate than in the US; as a result, 97% of modern diesel cars exceed the official limit for NOx pollution. Behind the scenes, the British government has tried to block tougher testing. It’s a familiar story: the government similarly watered down plans to tackle childhood obesity in the face of special pleading from the food and drink industry.

The high court ruling puts the ball back in the government’s court. It should choose to accept it, rather than appeal. But either way, it has been exposed as a government willing to privilege marginal political advantage and the lobbying efforts of big business over the health of the nation.

Fasten your seat belts: Climate change could add to turbulence during air travel

Flight turbulence could increase significantly under climate change, a study warns, potentially upping the risk of injury — or at least flight anxiety — for future airline passengers. Furthermore, fuel and maintenance costs for carriers could rise.

http://www.bendbulletin.com/nation/5214806-151/fasten-your-seat-belts-climate-change-could-add

An increase in atmospheric carbon dioxide concentrations could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence, suggests the research conducted by atmospheric scientist Paul Williams of the University of Reading.

By the middle of the century, with no effort to reduce atmospheric concentrations of carbon dioxide, the volume of airspace experiencing light turbulence would increase by about 59 percent.

Airspace experiencing severe turbulence could increase by anywhere from 36 percent to 188 percent, the study found.

“We’re particularly interested in severe turbulence, because that’s the kind of turbulence that’s strong enough to hospitalize people,” Williams told The Washington Post.

Forecasting algorithms can help pilots anticipate and avoid turbulent patches. But the research does suggest that future fliers could be in for a bumpier ride.

The paper builds on a 2013 study in the journal Nature Climate Change by Williams and colleague Manoj Joshi of the University of East Anglia, which found an increase in moderate-to-severe turbulence in the North Atlantic as a result of climate change.

The study did not investigate the effects on lighter or more severe degrees of turbulence. In the new paper, Williams expanded the study to light turbulence, and more severe conditions.

Light turbulence typically comes with only minor discomfort for passengers, perhaps an increase in nausea or anxiety. Severe turbulence has been known to cause injuries and even hospitalizations.

Williams focused on an area in the North Atlantic known for heavy air traffic, particularly between Europe and North America, and limited his simulations to winter, when turbulence is known to be at its highest.

He examined 21 different wind-related characteristics known to be indicators of air turbulence levels, including wind speed and changes in air flow direction.

The study found an increase in turbulence across the spectrum. Light turbulence was projected to increase by an average of 59 percent, light-to-moderate by 75 percent, moderate by 94 percent, moderate-to-severe by 127 percent and severe by 149 percent, although there’s substantial uncertainty associated with the more severe categories.

Williams stressed that severe turbulence would remain rare — even with the increase. But even an increase in light turbulence can cause greater wear and tear on planes or force pilots to use extra fuel redirecting their flight paths to avoid rough patches.

The increase in air turbulence may apply only to the North Atlantic, researchers not involved in the study said.

“Regional variations of this increase may be quite uncertain, particularly in the higher latitudes where other aspects of circulation change that are less well understood and more model-dependent may dominate,” said Isla Simpson, a scientist at the National Center for Atmospheric Research, in an emailed comment to The Post.

Kristopher Karnauskas, an atmospheric and oceanic sciences expert at the University of Colorado at Boulder, said the behavior of the jet stream over the Pacific may respond differently to climate change.

The study builds on an area of climate science that increasingly suggests rising global temperatures can cause changes in atmospheric airflow, including shifts in major air currents known as jet streams.

Because the equator is the warmest part of the planet, and warm air takes up more space than cold air, the atmosphere tends to be thicker around the center of Earth than at the poles. As a result, there’s a kind of downhill atmospheric slope from the equator to the poles over which air flows. While this is happening, Earth is constantly spinning, pushing airflow eastward. In the North Atlantic, the result is a jet stream — a meandering, wavy current flowing around the planet from west to east.

As the planet grows hotter, however, warming air near the surface could bring about changes in the atmospheric slope between equator and poles. Models such as the one used in Williams’ new paper have suggested that the jet stream could become stronger as a result, bringing about an increase in the types of wind patterns that lead to increased air turbulence.

Some research has already begun to detect changes in large-scale atmospheric currents. Other scientists have suggested that rapid warming in the Arctic is actually causing the jet stream to weaken.

There remains considerable uncertainty about how airflow near Earth’s surface might change in the future, Simpson said. But she said scientists are becoming more confident about the changes “that we expect to happen higher up, near the altitude where planes fly.”

Examining these issues can lead to a better understanding of the effects of climate change on aviation, Karnauskas said.

“I think it’s been decades that all of the attention has been on the impact of such industries like aviation on climate, but this is something that’s flipping it around and looking at the impact of climate on aviation,” he said. “If we can really understand the two-way street that we’re dealing with, that’s really going to help us understand ultimately how the climate will change in the future as a coupled system between the people and the atmosphere.”

Combined effect of brighter sun and CO₂ emissions could lead to unprecedented warming

The same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide due to the sun becoming stronger, experts warn

http://www.independent.co.uk/environment/co-sun-emissions-global-warming-a7667401.html

Carbon dioxide concentrations are heading towards values not seen in the past 200 million years. The sun has also been gradually getting stronger over time. Put together, these facts mean the climate may be heading towards warmth not seen in the past half a billion years.

A lot has happened on Earth since 500,000,000BC. Continents, oceans and mountain ranges have come and gone, and complex life has evolved and moved from the oceans onto the land and into the air. Most of these changes occur on very long timescales of millions of years or more. However, over the past 150 years global temperatures have increased by about 1°C, ice caps and glaciers have retreated, polar sea ice has melted, and sea levels have risen.

Some will point out that Earth’s climate has undergone similar changes before. So what’s the big deal this time?

Scientists can seek to understand past climates by looking at the evidence locked away in rocks, sediments and fossils. What this tells us is that yes, the climate has changed in the past, but the current speed of change is highly unusual. For instance, carbon dioxide hasn’t been added to the atmosphere as rapidly as today for at least the past 66m years.

In fact, if we continue on our current path and exploit all convention fossil fuels, then as well as the rate of CO₂ emissions, the absolute climate warming is also likely to be unprecedented in at least the past 420m years. That’s according to a new study we have published in Nature Communications.

In terms of geological time, 1°C of global warming isn’t particularly unusual. For much of its history the planet was significantly warmer than today, and in fact more often than not Earth was in what is termed a “greenhouse” climate state. During the last greenhouse state 50m years ago, global average temperatures were 10-15°C warmer than today, the polar regions were ice-free, palm trees grew on the coast of Antarctica, and alligators and turtles wallowed in swamp-forests in what is now the frozen Canadian Arctic.

In contrast, despite our current warming, we are still technically in an “icehouse” climate state, which simply means there is ice on both poles. The Earth has naturally cycled between these two climate states every 300m years or so.

Just prior to the industrial revolution, for every million molecules in the atmosphere, about 280 of them were CO₂ molecules (280 parts per million, or ppm). Today, due primarily to the burning of fossil fuels, concentrations are about 400 ppm. In the absence of any efforts to curtail our emissions, burning of conventional fossil fuels will cause CO₂ concentrations to be around 2,000ppm by the year 2250.

This is of course a lot of CO₂, but the geological record tells us that the Earth has experienced similar concentrations several times in the past. For instance, our new compilation of data shows that during the Triassic, around 200m years ago, when dinosaurs first evolved, Earth had a greenhouse climate state with atmospheric CO₂ around 2,000-3,000ppm.

High concentrations of carbon dioxide don’t necessarily make the world totally uninhabitable: the dinosaurs thrived, after all.

But that doesn’t mean this is no big deal. For a start, there is no doubt that humanity will face major socio-economic challenges dealing with the dramatic and rapid climate change that will result from the rapid rise to 2,000 or more ppm.

But our new study also shows that the same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide. This is because the Earth’s temperature does not just depend on the level of CO₂ (or other greenhouse gases) in the atmosphere. All our energy ultimately comes from the sun, and due to the way the sun generates energy through nuclear fusion of hydrogen into helium, its brightness has increased over time. Four and a half billion years ago when the Earth was young the sun was around 30 per cent less bright.

What really matters is the combined effect of the sun’s changing strength and the varying greenhouse effect. Looking through geological history we generally found that as the sun became stronger through time, atmospheric CO₂ gradually decreased. On average, both changes cancelled each other out.

But what about in the future? We found no past time period when the drivers of climate, or climate forcing, was as high as it will be in the future if we burn all the readily available fossil fuel. Nothing like it has been recorded in the rock record for at least 420m years.

A central pillar of geological science is the uniformitarian principle: that “the present is the key to the past”. If we carry on burning fossil fuels as we are at present, by 2250 this old adage is sadly no longer likely to be true. It is doubtful that this high-CO₂ future will have a counterpart, even in the vastness of the geological record.

Gavin Foster is a professor of isotope geochemistry at the University of Southampton, Dana Royer is a professor of earth and environmental sciences at Wesleyan University and Dan Lunt is a professor of climate science at the University of Bristol. This article first appeared on The Conversation (theconversation.com)

Extreme weather events linked to climate change impact on the jet stream

On the is an image of the global circulation pattern on a normal day. On the right is the image of the global circulation pattern when extreme weather occurs. The pattern on the right shows extreme patterns of wind speeds going north and south, while the normal pattern on the left shows moderate speed winds in both the north and south directions. Credit: Michael Mann, Penn State

On the is an image of the global circulation pattern on a normal day. On the right is the image of the global circulation pattern when extreme weather occurs. The pattern on the right shows extreme patterns of wind speeds going north and south, while the normal pattern on the left shows moderate speed winds in both the north and south directions. Credit: Michael Mann, Penn State

Unprecedented summer warmth and flooding, forest fires, drought and torrential rain—extreme weather events are occurring more and more often, but now an international team of climate scientists has found a connection between many extreme weather events and the impact climate change is having on the jet stream.

https://phys.org/news/2017-03-extreme-weather-events-linked-climate.html

“We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events,” said Michael Mann, distinguished professor of atmospheric science and director, Earth System Science Center, Penn State. “Short of actually identifying the events in the climate models.”

The unusual weather events that piqued the researchers’ interest are things such as the 2003 European heat wave, the 2010 Pakistan flood and Russian heatwave, the 2011 Texas and Oklahoma heat wave and drought and the 2015 California wildfires.

The researchers looked at a combination of roughly 50 climate models from around the world that are part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), which is part of the World Climate Research Programme. These models are run using specific scenarios and producing simulated data that can be evaluated across the different models. However, while the models are useful for examining large-scale climate patterns and how they are likely to evolve over time, they cannot be relied on for an accurate depiction of extreme weather events. That is where actual observations prove critical.

The researchers looked at the historical atmospheric observations to document the conditions under which extreme weather patterns form and persist. These conditions occur when the jet stream, a global atmospheric wave of air that encompasses the Earth, becomes stationary and the peaks and troughs remain locked in place.

“Most stationary jet stream disturbances, however, will dissipate over time,” said Mann. “Under certain circumstances the wave disturbance is effectively constrained by an atmospheric wave guide, something similar to the way a coaxial cable guides a television signal. Disturbances then cannot easily dissipate, and very large amplitude swings in the jet stream north and south can remain in place as it rounds the globe.”

This constrained configuration of the jet stream is like a rollercoaster with high peaks and valleys, but only forms when there are six, seven or eight pairs of peaks and valleys surrounding the globe. The jet stream can then behave as if there is a waveguide—uncrossable barriers in the north and south—and a wave with large peaks and valleys can occur.

“If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, and lasting rains can lead to flooding,” said Stefan Rahmstorf, Potsdam Institute for Climate Impact Research (PIK), Germany.

The structure of the jet stream relates to its latitude and the temperature gradient from north to south.

Temperatures typically have the steepest gradients in mid-latitudes and a strong circumpolar jet stream arises. However, when these temperature gradients decrease in just the right way, a weakened “double peak” jet stream arises with the strongest jet stream winds located to the north and south of the mid-latitudes.

“The warming of the Arctic, the polar amplification of warming, plays a key role here,” said Mann. “The surface and lower atmosphere are warming more in the Arctic than anywhere else on the globe. That pattern projects onto the very temperature gradient profile that we identify as supporting atmospheric waveguide conditions.”

Theoretically, standing jet stream waves with large amplitude north/south undulations should cause unusual weather events.

“We don’t trust climate models yet to predict specific episodes of extreme weather because the models are too coarse,” said study co-author Dim Coumou of PIK.

“However, the models do faithfully reproduce large scale patterns of temperature change,” added co-author Kai Kornhuber of PIK.

The researchers looked at real-world observations and confirmed that this temperature pattern does correspond with the double-peaked jet stream and waveguide patter associated with persistent extreme weather events in the late spring and summer such as droughts, floods and heat waves. They found the pattern has become more prominent in both observations and climate model simulations.

“Using the simulations, we demonstrate that rising greenhouse gases are responsible for the increase,” said Mann. The researchers noted in today’s (Mar. 27) issue of Scientific Reports that “Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability.”

“We are now able to connect the dots when it comes to human-caused global warming and an array of extreme recent weather events,” said Mann.

While the models do not reliably track individual extreme weather events, they do reproduce the jet stream patterns and temperature scenarios that in the real world lead to torrential rain for days, weeks of broiling sun and absence of precipitation.

“Currently we have only looked at historical simulations,” said Mann. “What’s up next is to examine the model projections of the future and see what they imply about what might be in store as far as further increases in extreme weather are concerned.”