Cooling Pacific has dampened global warming, research shows

Research explains why changes in tropical waters could be responsible for recent 'pause' in rising temperatures 

Fiona Harvey 

theGuardian.com, Thursday 29 August 2013

Cooling waters in the tropical Pacific Ocean appear to be a major factor in dampening global warming in recent years, scientists said on Wednesday.

Their work is a big step forward in helping to solve the greatest puzzle of current climate change research – why global average surface temperatures, while still on an upward trend, have risen more slowly in the past 10 to fifteen years than previously.

Waters in the eastern tropical regions of the Pacific have been notably cooler in recent years, owing to the effects of one of the world's biggest ocean circulatory systems, the Pacific decadal oscillation.

Many people are aware of the El Niño and La Niña weather systems, which affect the Pacific and bring hotter and stormier or cooler weather in cycles of just a few years, and can have a strong effect on global weather. But few are aware that both of these systems are just part of the much bigger Pacific decadal oscillation, which brings warmer and cooler weather over decades.

The system is now in a cooling phase, scientists have noted, which could last for years. The last such phase was from the 1940s to the 1970s.

The new study by the Scripps Institution of Oceanography and supported by the US government's National Oceans and Atmospheric Administration (NOAA), published in the journal Nature, has linked the "pause" in global warming with the Pacific oscillation.

Dan Barrie, programme manager at NOAA, called the research "compelling" and said: "[It] provides a powerful illustration of how the remote eastern tropical Pacific guides the behaviour of the global ocean-atmosphere system, in this case exhibiting a discernible influence on the recent hiatus in global warming."

In winter, the effect of the cooler phase of the oscillation on the northern hemisphere is to depress temperatures slightly; but in summer, the cooler waters in the equatorial Pacific have less impact on the northern hemisphere's weather. The scientists, using computer models, compared their results with observations and concluded that global average annual temperatures have been lower than they would otherwise have been because of the oscillation. But the observed higher summer temperatures of recent years show more of the true effects of global warming, according to the research. Global average temperatures are taken over the whole year, obscuring the effect of this seasonal variation.

Shang-Ping Xie, professor of environmental science at Scripps, said: "In summer, the equatorial Pacific's grip on the northern hemisphere loosens, and the increased greenhouse gases continue to warm temperatures, causing record heat waves and unprecedented Arctic sea ice retreat."

Dr Alex Sen Gupta, of the Climate Change Research Centre at the University of New South Wales, who was not part of the study team, said: "The authors have set up some elegant experiments using a climate model to test whether a natural oscillation that has gone through a large swing in the tropical Pacific Ocean over the last decade can explain the recent halt in surface global warming … the new simulation accurately reproduces the timing and pattern of changes that have occurred over the last four decades with remarkable skill. This clearly shows that the recent slowdown is a consequence of a natural oscillation."

The role of oceans in regulating the planet's temperatures has taken on a greater significance in climate change research, as not enough is yet known about how ocean currents and the circulation of warmer surface water to the deep oceans below affect the weather and climate.

Research indicates that oceans have absorbed much of the heat and about a third of the additional carbon dioxide pumped into the air from pre-industrial times. This has an effect – the thermal expansion of the oceans is likely to be the biggest factor behind sea level rise, and the absorption of carbon dioxide is making the oceans more acidic.

Scientists also think that the circulation of heat from the top layers of the ocean, which have been most affected to date, to the deeper oceans below may be another factor behind the "hiatus" in global warming. What the full effects of this exchange of energy may be, particularly on ocean currents, is not yet known.

Researchers have called for more observations of the ocean, including many more buoys and underwater readings.

The slowdown in the upward march of global average temperatures has been greeted by climate sceptics as evidence that the climate is less affected by greenhouse gases than thought. But climate scientists are much more cautious, pointing out that the trend is still upwards, and that the current temperature rises are well within the expected range. Past temperature records and computer predictions both show that periods of slower rises are to be expected as part of the natural variability of the planet's climate.

These issues are likely to be a major focus of the forthcoming report by the Intergovernmental Panel on Climate Change (IPCC), the body of scientists who produce the most authoritative and comprehensive summaries of climate research. Their eagerly awaited fifth report, seven years since the last, will be published next month. It is likely to affirm that scientists are more certain than ever – at least 95%, up from 90% previously – that climate change is happening and is mostly caused by human actions, but it may suggest that the climate is slightly less sensitive to carbon than some outlying research has posited. That may mean that some of the highest estimates of future temperature rises, of more than 6C within several decades, are less likely, but it does not let the world off the hook – warming of more than 2C is still highly likely on current high emissions trends, and that would cause severe consequences around the world.

A discussion of the recent "hiatus" in temperature rises, and its causes, will form an important part of the IPCC report. However, as the main source papers for the IPCC had to be gathered some time ago, the Scripps-led study of the Pacific decadal oscillation will not have made it into the final report, the first part of which will be presented at a meeting in Stockholm next month.

The Scripps research team said the current cooling phase in the Pacific began just after a strong El Niño year in 1998, but that it was not possible to predict when it might end.

They arrived at the conclusion by using innovative computer modeling methods to simulate regional patterns of climate anomalies. This enabled them to see global warming in greater spatial detail, revealing where it has been most intense and where there has been no warming or even cooling.

They developed new computer models that could show regional and seasonal variations in temperature, as well as global patterns. "Climate models consider anthropogenic forcings like greenhouse gases and tiny atmospheric particles known as aerosols, but they cannot study a specific climate event like the current hiatus," said Yu Kosaka, co-author of the Nature paper. "We devised a new method for climate models to take equatorial Pacific ocean temperatures as an additional input."

When these were taken into account, the models predicted the temperature changes observed, including the current "hiatus" in the upward climb of temperatures.

The scientists warned, however, that when the current cooling phase turns, the upward march of temperatures is likely to resume, perhaps at faster rates than before as greenhouse gas emission rates are higher.

Xie said: "We don't know precisely when we're going to come out of [the hiatus] but we know that over the timescale of several decades, the climate will continue to warm as we pump more greenhouse gases into the atmosphere."

Some of the effects of the cooling in the Pacific are not straightforward – drier temperatures in the US midwest are one of the associated results.

During the last cool phase, warmer, drier weather dominated in the midwestern US, as it has in the past 15 years with a serious drought prevailing through much of the region for much of the time.

How extreme will future heatwaves be? Choose your own adventure

Depending on our greenhouse gas emissions path, today's extreme heat could become the norm, or could be relatively rare

John Abraham & Dana Nuccitelli

The Guardian, 23 August 2013

Dim Coumou and Alexander Robinson from the Potsdam Institute for Climate Impact Research have published a paper in Environmental Research Letters (open access, free to download) examining the frequency of extreme heat events in a warming world.

They compared a future in which humans continue to rely heavily on fossil fuels (an IPCC scenario called RCP8.5) to one in which we transition away from fossil fuels and rapidly reduce greenhouse gas emissions (called RCP2.6). In both cases, the global land area experiencing extreme summer heat will quadruple by 2040 due to the global warming that's already locked in from the greenhouse gases we've emitted thus far.

However, in the low emissions scenario, extreme heat frequency stabilizes after 2040 (left frames in Figure 1), while it becomes the new norm for most of the world in the high emissions, fossil fuel-heavy scenario (right frames in Figure 1) (click here for a larger version).

Figure 1: Multi-model mean of the percentage of boreal summer months in the time period 2071–2099 with temperatures beyond 3-sigma (top) and 5-sigma (bottom) under low emissions scenario RCP2.6 (left) and high emissions RCP8.5 (right).

Coumou & Robinson looked at the frequency of rare and extreme (3-sigma, meaning 3 standard deviations hotter than the average) and very rare and extreme (5-sigma) temperature events. 3-sigma represents a 1-in-370 event, and 5-sigma is a 1-in-1.7 million event.

As shown in the video below from NASA, summer temperatures have already begun to shift significantly towards more frequent hot extremes over the past 50 years. What used to be a rare 3-sigma event has already become more commonplace.

Summer temperatures shifting to hotter averages and extremes between the 1950s and 2000s. Source: NASA/Goddard Space Flight Center GISS and Scientific Visualization Studio

Coumou & Robinson point out that these 3-sigma events have tended to have very damaging consequences:

"most of the 3-sigma extremes that have occurred in recent years resulted in serious impacts to society, causing many heat-related deaths, massive forest fires or harvest losses"

Coumou pointed to the Moscow summer heat wave of 2010 as a good example of a damaging 3-sigma extreme heat event. Thousands died during that heat wave, and the associated drought cut Russia's wheat crop by 40 percent, cost the nation $15 billion, and led to a ban on grain exports, causing food prices to rise globally.

"In the Moscow region the average temperature for the whole of July was around 7°C [13°F] warmer than normal – it was around 25°C [77°F]. In some parts, temperatures above 40°C [104°F] were measured"

As Figure 1 above shows, if we continue to rely heavily on fossil fuels (right frames), these extreme heat events will occur throughout the summer for most of the global land area by the late 21st century, especially in the tropics. Currently, around 5 percent of the world's land mass is experiencing a 3-sigma event at any one time during the summer months.

In the high greenhouse gas emissions scenario, most of Africa, Central America, and northern South America will experience 3-sigma extreme heat events for close to 100 percent of the summer. They will become the norm. Even extreme 5-sigma heat events, which are currently exceptionally rare, will become relatively commonplace, especially near the equator.

On the other hand, in the scenario where we take major steps to reduce human greenhouse gas emissions (left frames in Figure 1), 3-sigma events will still be relatively rare by the late 21st century, especially outside of the tropics. Extreme 5-sigma events will become somewhat more commonplace near the equator, but will remain fairly rare occurrences globally.

In short, damaging summer extreme heat events are going to become more commonplace, but just how much more commonplace is up to us. While it's difficult to determine how climate change will impact some types of extreme weather (tornadoes, for example), the link between global warming and heat waves is quite clear. Increasing global temperatures will make (and have already made) extreme heat events more commonplace.

The longer we continue to rely on fossil fuels and the higher our greenhouse gas emissions, the more extreme heat we'll lock in. If we manage to take serious action to reduce our greenhouse gas emissions, we can limit global warming to a level where extreme heat events will become more commonplace, but to a level we can manage to adapt to.

If we continue our reliance on fossil fuels and associated greenhouse gas emissions growth, we'll commit ourselves to a world where today's most extreme heat waves become the norm, and future extreme heat makes today's heat waves look downright balmy.

It's in our hands which future scenario becomes reality. It's like one of those choose your own adventure books, but real. Which future will we choose?

How to have zero emissions housing – and tiny power bills – in ten years

The Conversation, 8 August 2013

Dominique Hes, Senior Lecturer in Sustainable Architecture at University of Melbourne

A new study says that all Australia's existing housing could be retrofitted to be zero emissions within ten years. Households could halve their energy use and go gas free. Australian households currently spend approximately A$15 billion every year on electricity and gas bills: this could be largely eliminated. Making this change would not only meet our emissions reduction targets but place Australia as a leader in a future carbon-constrained world.

The plan, launched today by Beyond Zero Emissions (BZE) as part of the Zero Carbon Australia project, is a follow up to the Stationary Energy Plan, which showed how Australia's electricity could be supplied by 100% renewable energy sources within 10 years.

Most Australian homes are based on designs from a time when energy was cheap and plentiful, and we weren't aware of the impact CO₂ was having on our climate. Consequently, Australian homes are poorly built for our conditions, wasteful and often uncomfortable. But we can fix them with technology we've already got.

Energy freedom

The key points for households are:

• Energy use could be halved. This would be partly through simple improvements in design, such as better insulation, better windows and doors that keep heat where we want it, shading, and reflective roof paint to keep houses cool. Uncontrolled draughts would be replaced with controlled ventilation. The rest would be done with more efficient appliances: electric heat pumps for heating and hot water (these are considerably more efficient than gas), induction cooking and LED lighting.

• Households could go gas-free, switching gas appliances for higher-efficiency electric appliances. Why switch off gas? While it's lower emissions than coal-fired electricity, it's much higher emissions than electricity from renewable sources.

• Households could become renewable electricity power stations, through use of rooftop solar panels. Beyond Zero Emissions' previous report on stationary energy shows all households should be able to be powered from renewables. This has been backed up by more recent reports from other sources.

• Houses could be cosier in winter, cooler in summer, and healthier year-round.

Businesses could also reduce energy use by extensive retrofitting and by installing solar cells on rooftops. This in combination with the elimination of gas is shown to reduce energy use by half with the installation costing no more than business as usual.

All of these would have a significant impact on our energy related emissions. And the retrofitting work for households alone would create around 50,000 jobs in the trades sector.

How do we get there?

The plan is ambitious, but the barriers to achieving it aren't technological: we have everything we need to make it happen.

There are financial barriers for individual households and businesses. To achieve the plan, households particularly will need incentives or ways to offset initial costs against future savings. For example, interest-free loans could be given to carry out the work, or retrofits could form part of a household energy agreement with their retailer.

And of course, there are sizable economic and political hurdles; for example, to eliminating the use of gas. Gas is a significant industry in Australia, and re-purposing infrastructure, technology, resources – and most importantly jobs – needs to be approached carefully or the good intentions will be met by anger.

Other industries will be affected, including electricity and most importantly, energy exports. Policies of energy reduction in Australia will need to extend to our coal and gas export sector or we will be seen as hypocrites. Without a global approach, our emissions reductions efforts will be ineffectual.

But with international action on energy and carbon growing, and limited non-renewable resources, transition in fossil fuel sectors is inevitable. Australia can benefit from leading the pack, rather than following or being forced into a corner by international or natural restrictions.

Australia has committed to reducing its emissions. While aiming for a zero carbon country in any time frame is way beyond what is in any current policy, reports like this show we can radically improve on current clean energy and climate policies. We have the technology.

The good news is transitioning to this sort of world has become easier and cheaper as technology improves. Moving to 100% renewable energy is now A$37 billion cheaper compared to the figures reached in Beyond Zero Emissions's previous report on stationary energy.

It is now time to deal with the non-technical social and political aspects that require strong leadership. You may look at this report and think "but that will never happen". The challenge is this: assume it can be done and then find a way to do it.

Extreme weather likely to increase and intensify, Senate report finds

Peter Hannam, Carbon economy editor   

The Age, August 7, 2013 

Note: A second Senate Inquiry Report, Effectiveness of threatened species and ecological communities' protection in Australia has also been released

The extreme weather events that have hit Australia in recent years are likely to increase in frequency and potentially intensify in the future as a result of climate change, a Senate inquiry has found.

The inquiry, Recent trends in and preparedness for extreme weather events, recommended increased co-ordination across governments and many sectors of society to prepare for and limit the impact of such events.

The Senate committee report also called for "credible and reliable flood mapping" to assist landowners of potential risks and to better inform land-use planning laws.

The report will likely be welcomed by the insurance industry in particular, which had been calling for many of the changes it recommends. These include toughening building codes to "account for foreseeable risks", and removing disincentives for taking up insurance, such as state taxes.

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The cost of so-called catastrophe claims from floods, cyclones, bush fires and other such events was $8.8 billion in the three years to March 2013, according to the Insurance Council of Australia. The sum included $5.4 billion in 2011 alone.

"These events are becoming more expensive," the ICA spokesman said. "The driver of this is that more and bigger homes are being built in disaster-prone areas, such as flood plains." "Much of [the cost] could have been avoided if the damaged properties had been built to be resilient to the risks."

Hot times

Some of the report's submissions were made in the first weeks of 2013, the country's hottest period on record. January, for instance, broke records for the hottest average maximum temperature nationwide, the hottest single month on record, and was part of Australia's hottest summer.

The report's release Wednesday also comes after the US released its State of the Climate report for 2012, which found last year to be the eighth or ninth hottest in data series going back to 1850. It noted many other signals of a warming planet, including record low Arctic ice cover and the 22nd consecutive year of shrinking glacier mass.

The Greens jumped on the Senate committee's findings, saying it was time Labor and the Coalition acknowledged Australia "is unprepared for a significant increase in natural disasters as a result of climate change".

"It's time Kevin Rudd and Tony Abbott stopped treating natural disasters as one-off events," Greens Leader Senator Christine Milne said. "Australia needs to prepare for a permanent state of extreme weather."

The Greens have proposed lifting annual spending mitigation efforts to prepare for floods, droughts and other extreme events seven-fold to $350 million, with the plan to be funded by a $2-per-tonne levy on exports of coal burnt in power stations.

"We will obviously consider an extensive report carefully," said Greg Hunt, the Coalition's spokesman for climate change.

Mr Hunt singled out the inquiry's recommendations that the government work closely with the CSIRO and the Bureau of Meteorology to step up research into early warning of extreme events and also the links between weather events and climate trends.

"I have a deep respect for and belief in the work of both the Bureau of Meteorology and CSIRO," Mr Hunt said. "We therefore strongly support continued and extended research by both into climatic trends, weather events and climate change."

Fairfax Media has sought a response from Mark Butler, the Minister for Climate Change. 

Insurer support

The report found that Australia's exposure to extreme events is increasing not just from climate change but also because of the spread of population and investments into vulnerable areas.

The attention to those threats has been welcomed by insurers.

"Today's report is another voice that strongly says we need a comprehensive and more sustainable approach to managing natural disasters in Australia to keep people safe," said Mike Wilkins, chief executive of IAG, one of Australia's biggest insurers.

"Every Australian is impacted by natural disasters and extreme weather," Mr Wilkins said. "Whether it be through personal devastation in losing loved ones or property, whether it be through billions of their taxpayer dollars spent on recovery, the creation of special flood levies, or through higher insurance premiums, we all pay the price when we fail to make where we live as safe as possible."

Beyond science

Mark Stafford Smith, from CSIRO's Climate Adaptation Flagship, said the strongest signals of climate change affecting Australia included hotter temperatures and rising sea levels.

Heat records for maximums, for instance, were falling at three times the rate for those involving cold temperatures over the past decade or so. New minimum temperature records were five times as likely to be for warmth as for cold conditions.

"If nothing was happening, you'd expect them to be roughly equal," Dr Stafford Smith said.

Rising temperatures were also contributing to ''a significant increase'' in bushfire danger, he said.

While other signals were less clear, such as the frequency of heavy rainfall events, ''responsible managers'', including governments, would be looking to reduce risks and improve the resilience of infrastructure, he said. Political leaders and the wider community would have to make a call on the right balance, a tough challenge given that some of the science of climate change will remain uncertain.

"How much do we want to invest today for future generations as opposed to putting it into our own well-being?" Dr Stafford Smith said. ''That's a genuine societal value trade-off that no science can answer.''