Extreme weather: it's about to get worse, says scientists

The Age, March 29, 2012

Global warming is leading to such severe storms, droughts and heatwaves that nations should prepare for an unprecedented onslaught of deadly and costly weather disasters, an international panel of climate scientists says in a new report.

The greatest danger from extreme weather is in highly populated, poor regions of the world, the report warns, but no corner of the globe - from Mumbai to Miami - is immune. The document by a Nobel Prize-winning panel of climate scientists forecasts stronger tropical cyclones and more frequent heat waves, deluges and droughts.

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The 594-page report blames the scale of recent and future disasters on a combination of man-made climate change, population shifts and poverty.

In the past, the Intergovernmental Panel on Climate Change, founded in 1988 by the United Nations, has focused on the slow inexorable rise of temperatures and oceans as part of global warming.

This report by the panel is the first to look at the less common but far more noticeable extreme weather changes, which recently have been costing on average about $US80 billion ($A76.75 billion) a year in damage.

"We mostly experience weather and climate through the extreme," said Stanford University climate scientist Chris Field, who is one of the report's top editors. "That's where we have the losses. That's where we have the insurance payments. That's where things have the potential to fall apart.

"There are lots of places that are already marginal for one reason or another," Field said. But it's not just poor areas: "There is disaster risk almost everywhere."

The scientists say that some places, particularly parts of Mumbai in India, could become uninhabitable from floods, storms and rising seas. In 2005, over 24 hours nearly one metre of rain fell on the city, killing more than 1000 people and causing massive damage. Roughly 2.7 million people live in areas at risk of flooding.

Other cities at lesser risk include Miami, Shanghai, Bangkok, China's Guangzhou, Vietnam's Ho Chi Minh City, Burma's Rangoon and India's Kolkata. The people of small island nations, such as the Maldives, may also need to abandon their homes because of rising seas and fierce storms.

"The decision about whether or not to move is achingly difficult and I think it's one that the world community will have to face with increasing frequency in the future," Field said in a telephone news conference.

The study says forecasts that some tropical cyclones - which includes hurricanes in the United States - will be stronger because of global warming, but the number of storms should not increase and may drop slightly.

Some other specific changes in severe weather that the scientists said they had the most confidence in predicting include more heatwaves and record hot temperatures worldwide, increased downpours in Alaska, Canada, northern and central Europe, East Africa and north Asia.

No emission limit on new coal plants

Tom Arup 

The Age, March 28, 2012

THE Baillieu government has dropped an election commitment to bring in limits on greenhouse gas emissions from new coal-fired power plants.

The decision by Energy Minister Michael O'Brien came just hours after the government announced it would shed the state's goal to reduce greenhouse gas emissions by 20 per cent by the end of the decade.

It also came as the state government released a report on future impacts of climate change in Victoria, finding average temperatures could increase by 1 to 4.2 degrees by 2070 relative to 1990.

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The new coal power standards - proposed by the previous Labor government and supported by the Coalition - would have capped emissions from new coal-fired power plants at 0.8 tonnes of carbon dioxide for every megawatt hour of electricity generated. They would also have required new plants to be ready to install clean coal technology if it became viable.

The federal government dumped similar national standards in December, saying the introduction of its carbon tax had made them redundant.

Mr O'Brien pointed to the Commonwealth's decision as a reason not to go ahead with the Victorian standards.

''The Commonwealth is not proceeding with such a restriction, nor do such restrictions apply to new coal-fired power stations in New South Wales or Queensland,'' he said.

''The combination of Commonwealth policies and market conditions have the practical effect that no new coal-fired power stations will be economically viable unless they are based on modern technology with significantly lower emissions.''

Labor's energy spokeswoman Lily D'Ambrosio said the decision showed ''this government clearly doesn't care about the environment or clean energy jobs''.

Energy Supply Association of Australia chief executive Matthew Warren backed the decision, saying it was ''sensible and unremarkable'' with a national carbon price in place.

But Environment Victoria's Mark Wakeham said ''polluters are welcome in Ted Baillieu's Victoria while the government is going out of its way to make it harder to build clean energy projects''.

The decision came as Victorian Climate Change Minister Ryan Smith said he would review the relevancy of other state climate programs in light of the national carbon tax.

''I would say certainly a number of programs are up for review, as the federal minister (Greg Combet) has asked us to review them as we are going to be talking about them in a few weeks' time,'' Mr Smith said.

Yesterday, he released an independent review of Victoria's Climate Change Act that recommends repealing the state's 20 per cent emissions target - which the state government has agreed to - because it would have no extra environmental benefit and would only lighten the load for other states in meeting a national 5 per cent emissions target.

The review also says that if the federal carbon pricing scheme is substantially amended or removed - as proposed by the federal opposition under Tony Abbott - then the merits of a state-based target should again be reviewed.

A separate report on Victorian climate change data was also released, finding the state's emissions have risen 0.9 per cent, or 1.1 million tonnes, between 2000 and 2009. Electricity generation produces 53 per cent of Victoria's total emissions.

The report also found that climate change may result in a substantial increase in the number of high-fire-danger days and might increase sea levels from 0.5 to 1.1 meters by 2100 across the state.

Climate change may also increase the number of days above 35 degrees in Victoria from nine in 1990 to between 15 and 26 in 2070. The extent and frequency of drought in Victoria may more than double by 2050, the report says.

Arctic sea ice maximum marks beginning of melt season

NSIDC, 26 March 2012

On March 18, 2012, Arctic sea ice extent reached its annual maximum extent, marking the beginning of the melt season for Northern Hemisphere sea ice. This year's maximum extent was the ninth lowest in the satellite record.

Overview of conditions

On March 18, 2012 Arctic sea ice likely reached its maximum extent for the year, at 15.24 million square kilometers (5.88 million square miles). The maximum extent was 614,000 square kilometers (237,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). The maximum occurred this year 12 days later than the 1979 to 2000 average date of March 6.

This year's maximum ice extent was the ninth lowest in the satellite record, slightly higher than the 2008 maximum (15.24 million square kilometers or 5.88 million square miles) Last year, 2011, was the lowest maximum on record, 14.64 million square kilometers (5.65 million square miles). Including this year, the nine years from 2004 to 2012 are the nine lowest maximums in the satellite record.

Conditions in context
As of March 23, ice extent has declined for five days. However, there is still a chance that the ice extent could expand again. Sea ice extent in February and March tends to be quite variable, because ice near the edge is thin and often quite dispersed. The thin ice is highly sensitive to weather, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year.

Arctic sea ice extent is declining in winter as well as in summer months, although the decline is not as steep in the winter months. At the beginning of April, NSIDC scientists will release a full analysis of winter conditions, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum.

Read more…

Trenberth: How To Relate Climate Extremes to Climate Change

Climate Progress

Posted: 25 Mar 2012

The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be….

The air is on average warmer and moister than it was prior to about 1970 and in turn has likely led to a 5–10 % effect on precipitation and storms that is greatly amplified in extremes. The warm moist air is readily advected onto land and caught up in weather systems as part of the hydrological cycle, where it contributes to more intense precipitation events that are widely observed to be occurring.

Kevin E. Trenberth, senior scientist, National Center for Atmospheric Research, in the journal Climatic Change, released under a Creative Commons-Attribution license (PDF here, HTML here)

Framing the way to relate climate extremes to climate change

Abstract

The atmospheric and ocean environment has changed from human activities in ways that affect storms and extreme climate events. The main way climate change is perceived is through changes in extremes because those are outside the bounds of previous weather. The average anthropogenic climate change effect is not negligible, but nor is it large, although a small shift in the mean can lead to very large percentage changes in extremes. Anthropogenic global warming inherently has decadal time scales and can be readily masked by natural variability on short time scales. To the extent that interactions are linear, even places that feature below normal temperatures are still warmer than they otherwise would be. It is when natural variability and climate change develop in the same direction that records get broken. For instance, the rapid transition from El Niño prior to May 2010 to La Niña by July 2010 along with global warming contributed to the record high sea surface temperatures in the tropical Indian and Atlantic Oceans and in close proximity to places where record flooding subsequently occurred. A commentary is provided on recent climate extremes. The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.

1 Introduction

How big is the human influence on climate? Is it big enough that a question such as "Is this event due to global warming?" even makes sense? Here these questions are addressed along with improved ways to frame the questions that inevitably arise when new climate extremes occur, and there have been many over the past 2 years. Clearly natural variability plays a major role. Accordingly a brief commentary on some of these extremes and how they relate to both natural variability and climate change is provided.

Climate change from human influences is difficult to perceive and detect because natural weather-related variability is large. Even with a significant climate change, most of the time, the weather is within previous bounds. However, human-induced climate change is persistent and tends to be in one direction, at least insofar as the increases in greenhouse gases are concerned (IPCC 2007). So one way of detecting such an influence is through long-term changes in mean conditions, preferably guided by climate model studies as to which variables and how they should change. This requires long averages to overcome the effects of natural variability (climate noise), and for quantities such as global temperatures, about 17 years is needed (Santer et al. 2011). With global warming, the thermodynamic variables have much stronger signal-to-noise ratios than dynamic variables (Deser et al. 2010). Accordingly, changes in temperature and the water holding capacity of the atmosphere are more robust than changes that depend on winds in any way.

If the problem is generalized to look at the entire probability distribution function (pdf) of the climate variables, then the biggest changes percentagewise occur in the tails of the distribution, where they can easily exceed several hundred percent (Trenberth 2011b). Accordingly, a change in climate is most likely to be perceived by encountering new "weather" and breaking records: changes in the extremes. Changes in certain extremes, such as higher temperatures and increases in heavy rains and droughts are expected with climate change (IPCC 2007; Trenberth 2011a).

Attribution (IPCC 2007; Stott et al. 2010) of the extremes requires a model to separate out the human influence from natural variability using numerical experimentation. This requires considerable integrity in the model's ability to simulate both, but models typically have great difficulty in simulating extremes well (Lin et al. 2006; Kharin et al. 2007) especially throughout the tropics for precipitation. In many model studies, the metric of Fraction of Attributable Risk (FAR) (e.g., Allen 2003) is used to express the fraction of risk of a particular threshold being exceeded. This is a relative rather than absolute metric.

However, methodological issues arise about the null hypothesis and where to assign the errors (Trenberth 2011b). The issue is whether the benefit of doubt errs on the side of natural variability (as has been the case) or on the side of a human influence.

Extremes are always expected to happen as the climate record gets longer, but certain extremes related to heating are becoming more evident. For example in the United States, extremes of high temperatures have been occurring at a rate of twice those of cold extremes (Meehl et al. 2009), and this has accelerated considerably since June 2010 to a factor of 2.7, and in the summer of 2011 to a factor of over 8 (Skolnik 2011). Texas, Oklahoma, New Mexico and Louisiana all suffered their hottest June-July-August (JJA) 2011 since 1895 (average temperature over 30 °C in Oklahoma and Texas), according to NOAA. Texas also experienced the driest JJA on record.

Climate extremes are typically treated individually, but many are not unrelated. The clustering of extremes occurs when natural variability creates anomalies that are in the same direction as global warming. This occurs especially in association with the dominant mode of natural variability: El Niño-Southern Oscillation (ENSO) during and following the warm El Niño phase (Trenberth et al. 2002) as heat leaves the ocean. During ENSO, large regional changes occur in Sea Surface Temperature (SST) throughout the tropics. Large positive SST anomalies in the central and eastern Pacific during El Niño tend to focus convective activity (thunderstorms, tropical storms, etc.) into those regions while suppressing activity elsewhere via both changes in atmospheric stability and wind shear. Meanwhile lighter winds and decreased evaporative cooling, and sunny skies in the tropical Atlantic and Indian oceans result in higher than normal SSTs 3–7 months after the peak SSTs in the Niño 3.4 region (Trenberth et al. 2002). As noted below, this happened in 2010 following the end of the El Niño in May 2010.

As climate varies or changes, several direct influences alter precipitation amount, intensity, frequency, and type (Trenberth et al. 2003; Trenberth 2011a). Warming accelerates land-surface drying as heat goes into evaporation of moisture, and this increases the potential incidence and severity of droughts, which has been observed in many places worldwide (Dai 2011). The moisture in the atmosphere, which has been widely observed to be increasing in association with increased SSTs, then gets carried around by atmospheric winds to where storms are favored. Typical storms reach out a distance of about three to five times the radius of the rain dimension, and gather in the water vapor, to produce precipitation. In weather systems, convergence of increased water vapor leads to more intense precipitation and the risk of heavy rain and snow events, but may also lead to reductions in duration and/or frequency of rain events, given that total amounts do not change much. The result is longer dry spells, as observed in the United States (Groisman and Knight 2008). Basic theory, climate model simulations, and empirical evidence all confirm that warmer climates, owing to increased water vapor, lead to more intense precipitation events even when the total annual precipitation is reduced slightly (Trenberth et al. 2007). A warmer climate therefore increases risks of both drought—where it is not raining—and floods—where it is—but at different times and/or places.

2 Is this extreme due to global warming?

Changes in atmospheric composition from human activities are the main cause of anthropogenic climate change by enhancing the greenhouse effect, although with important regional effects from aerosol particulates (IPCC 2007). Anthropogenic global warming inherently has decadal time scales and can be readily masked by natural variability over periods less than a decade or so. To the extent that interactions are linear, below normal temperatures can be fully consistent with climate change but are likely warmer than they otherwise would have been.

Globally on a day-to-day basis the climate change effects are 1–2 % of the natural energy flow, as elaborated on below. However, because global warming is always of one sign, a much bigger impact is from the cumulative effects of these radiative perturbations on the climate. The main memory is through the warming of the oceans, manifested in part through the ongoing rise in sea level, and the loss of Arctic sea ice and glacier mass. SSTs have risen by 0.5–0.6 °C since the 1950s, and over the oceans this has led to 4 % more water vapor in the atmosphere since the 1970s (Trenberth et al. 2007). As a result, the air is on average warmer and moister than it was prior to about 1970 and in turn has likely led to a 5–10 % effect on precipitation and storms that is greatly amplified in extremes. The warm moist air is readily advected onto land and caught up in weather systems as part of the hydrological cycle, where it contributes to more intense precipitation events that are widely observed to be occurring (IPCC 2007; Trenberth 2011a; Groisman and Knight 2008; Min et al. 2011; Pall et al. 2011).

The rationale for these numbers is as follows. The radiative forcing (IPCC 2007) is about 1.6 W m⁻² for both carbon dioxide increases alone and also the total with all other effects included (0.6–2.4 as 95 % confidence limits), and the net energy imbalance of the planet is estimated (Trenberth et al. 2009) to be 0.9 ± 0.5 W m⁻². The net energy flow through the climate system is equivalent to about 240 W m⁻². The difference between the net imbalance and the radiative forcing is because of the response of the climate system to the forcing, namely the warming of the planet and moistening of the atmosphere (Murphy et al. 2009). Water vapor is a powerful greenhouse gas. The increased water vapor roughly doubles the direct radiative forcing, giving the 1–2 % value, although this will vary from day to day. However, the average 4 % increase in water vapor becomes amplified in weather systems because it adds buoyancy to the air flowing into all storms, promoting them to become more intense and multiplying the effect (Trenberth et al. 2003; Trenberth 2011a). Instabilities can magnify effects further, although changes in wind shear and atmospheric stability as a consequence of the enhanced vertical motion may have reverse effects elsewhere. These lead to the approximate 5–10 % effect overall. For major droughts that last a month or longer, cumulative effects again become important as the absence of moisture means that all heating goes into sensible heating, creating higher temperatures, that in turn desiccate plants, and promote heat waves and wild fires. Lau and Kim (2012) quantify these effects for the Russian heat wave in 2010. During drought the memory stems from the changes in soil moisture.

Whether or not these values are accepted, the key point is that the anthropogenic climate change effect is not zero or negligible, nor is it large relative to the mean, but it is systematic. While natural variability clearly plays a major role in all events, such as those detailed below in 2010 and 2011, the record high SSTs did as well. In part the high SSTs were a consequence of the previous El Niño (Trenberth et al. 2002) but there is surely a significant global warming component (Gillett et al. 2008). Hence anthropogenic global warming has an identifiable role in the extreme weather (Trenberth and Fasullo 2012; henceforth TF12).

3 Some examples of recent climate extremes

3.1 SSTs

ENSO played a major role in climate extremes in 2010 and 2011 (TF12). El Niño conditions persisted through April 2010 but rapidly gave way to La Niña conditions by June. The SST anomalies for the northern summer (JJA) of 2010 (Fig. 1) reveals the La Niña conditions in the Pacific and hence the cooler than normal conditions mean that this was the region where the thunderstorms, tropical storms, and other convective activity were not occurring. However, as shown in TF12, very high SST anomalies from 0.5 to 1.5 °C, indeed record high SSTs in many instances (Fig. 1), occurred in the Indian Ocean and Indonesian region as well as throughout the tropical Atlantic (relative to a 1951–1970 normal that precedes most anthropogenic warming), regions that are normally very warm anyway (TF12). The total SSTs exceeded 29 °C over broad regions and were at an all time high in May 2010 (30.4 °C) in the northern Indian Ocean encompassing the Arabian Sea and Bay of Bengal (TF12). SSTs were also very high (second highest on record) north of Australia for September to November 2010, and by December they were the highest on record for that month. SST anomalies were also highest on record in the Gulf of Mexico in August 2010 and in the Caribbean in September 2010 (TF12). In 2011, SSTs were well above normal in the Gulf of Mexico in April but had cooled off by May. However, SSTs were still very high in the tropical Atlantic.

Because the water holding capacity of the atmosphere increases exponentially with temperature (e.g., Trenberth et al. 2003), a positive anomaly on top of already high SSTs has much greater effect than if located elsewhere. Indeed, the high SSTs were accompanied by very high water vapor amounts. The high SSTs provide ample moisture to the atmosphere and the resulting evaporative cooling of the ocean dropped the subsequent SST values down, but meanwhile heavy rains, often record breaking in intensity, occurred nearby to where the winds carried the moisture. This happened in China, India and Pakistan (June to early August 2010); Queensland, Australia (December 2010 and January 2011), and Colombia (October to December 2010) (Fig. 1). It also seems to have been a factor from 19 to 25 April 2011 when exceptionally heavy rains, exceeding 300 mm, occurred over southern Missouri, parts of Arkansas, eastern Oklahoma, and southern Illinois, and extended along the Ohio River Valley http://earthobservatory.nasa.gov/IOTD/view.php?id=50243, as a prelude to the flooding in the Mississippi.

3.2 La Niña and the Americas

La Niña conditions are well known to be associated with major anomalies in the Americas, and precipitation and flooding risk increase substantially in northern South America, such as in Colombia (Poveda et al. 2011). In La Niña summer and autumn the hurricane season is more active owing to a more favorable tropical circulation that allows storms to form in an environment of reduced wind shear and stability (Vecchi et al. 2008).

The SSTs (Fig. 1) in the Atlantic sector throughout the region north of Colombia were above 29 °C from July to September, and August 2010 was the warmest on record in both the Caribbean and in the Gulf of Mexico: anomalies exceeded 0.5–1.5 °C relative to the 1971–2000 base period (Fig. 1) (TF12). SST anomalies were especially large off the Colombian coast. The much cooler conditions to the west of the Central American isthmus both in absolute and anomaly terms understandably focused convective activity as a whole into the Atlantic and away from the Pacific. North of the equator, the result was a much above normal Atlantic hurricane season, in which there were 19 named storms, and 12 hurricanes, of which 4 were category 4 or 5, likely making it the second most active year after 2005. These aspects related to specific extremes are documented in TF12, including links between the heavy rains and the Russian heat wave of 2010, and the Colombian rains and the drought in the Amazon.

When La Niña is present, it strongly influences where the storms track across the United States, and the storms track in such a way as to miss the South. Consequently, Texas and surrounding areas (especially parts of Arizona, New Mexico and Oklahoma) suffered severe drought, and subsequently heat waves and wild fires in the northern spring and summer 2011. Nevertheless in spring, the storms crossing the central Midwest were able to link up with the warm moist air from the Gulf of Mexico, creating extra instability and buoyancy for the air that was entrained into the storms. This led to extensive heavy rains, flooding and tornado outbreaks. The pattern of rainfall in the spring is characteristic of La Niña although the extreme nature of the changes is not. The intense heat wave and "exceptional drought" continued in Texas through August. Many of these events are described in detail on line at the NOAA National Climatic Data Center, State of the Climate, Global Hazards site: http://www.ncdc.noaa.gov/sotc/hazards/2010/m (or 2011/m) where m is the month.

In spring, when land-sea contrasts transition to zero, strong westerly winds blow from the Pacific Ocean across the United States. Because the Rockies block the wind at low levels, the result is a strong westerly jet stream aloft while at low levels the air east of the Rockies comes from elsewhere including the Gulf of Mexico when there is a pronounced southerly component ahead of cold fronts. Both the change in wind speed and direction with height (southerlies at low levels, strong westerlies aloft) create wind shear, which sets the stage for super-cell thunderstorms to form tornadoes as the shear gets converted into rotation. According to NOAA, there were 539 deaths from over 1075 (actual count) tornadoes in April and May 2011 in the United States, the most deadly on record. Trends in the tornado record are not reliable, as increases in population over previously rural areas lead to more reporting of tornadoes, but the exceptional nature of the 2011 spring is not in doubt.

Global warming does not contribute directly to tornadoes themselves, but it does contribute to the vigor of the thunderstorms that host them through the increased warmth and moisture content (moist static energy) of the low level air flow. The increase in buoyancy of the air flowing through the Gulf of Mexico helps fuel the storms. Similarly, the extra moisture provided incremental amounts to the heavy rains that ultimately led to flooding along the Mississippi and later, farther north, heavy rains and melting snows contributed to extensive flooding of the Missouri River.

3.3 The Asian sector

The heavy rains and flooding in China, India, and Pakistan in JJA 2010 were associated with the very high SSTs to the south (Fig. 1) that provided extra moisture for the monsoon rains. The strong monsoon circulation then played a role in the Russian heat wave from mid-June to mid-August 2010 (Barriopedro et al. 2011; TF12), perhaps not unlike that in 2003 (Black and Sutton 2007) although influences from the Atlantic likely also played a role. The drought and famine in East Africa was also related to the high Indian Ocean SSTs (Williams and Funk 2011). Very large anomalies also existed at this time in Arctic sea ice and, in conjunction with positive Arabian Sea SST anomalies, connections to the events in Eurasia are suggested (Sedláček et al. 2011).

In the Asian sector, as the northern monsoon faded in late August of 2010, activity began to pick up in Australia, which switched to become very wet in September, continent wide, again reflecting the very high SSTs to the north (second highest on record), abundant moisture and the La Niña conditions. This was a fore-runner to the exceptionally heavy rains in Queensland in December 2010, and January 2011 where the southern monsoon rains kicked in with the presence of record high SSTs. Category 5 hurricane Yasi made landfall in Queensland in early February 2011.

4 Conclusions

The above commentary describes how natural variability in the presence of record high SSTs led to exceptional flooding events and extremes in 2010–11; see TF12 for details. Note that the La Niña in 2011–12 has different character owing to the absence of the high SSTs in the Indian and Atlantic Oceans. The SST changes feature contributions from climate change as well as strong regional contributions from ENSO.

The climate has changed; global warming is unequivocal (IPCC 2007) and human activities have undoubtedly changed the composition of the atmosphere and produced warming. Moreover there is no other plausible explanation for the warming. The human-induced changes are inherently multi-decadal and provide a warmer and moister environment for most weather events, even in the presence of large natural variability. In attribution studies, changing the null hypothesis from "there is no anthropogenic global warming effect" to one that recognizes the changed environment can completely change the outcome (Trenberth 2011b). In Bayesian statistics, this change might be thought of as a "prior".

Scientists are frequently asked about an event "Is it caused by climate change?" The answer is that no events are "caused by climate change" or global warming, but all events have a contribution. Moreover, a small shift in the mean can still lead to very large percentage changes in extremes. In reality the wrong question is being asked: the question is poorly posed and has no satisfactory answer. The answer is that all weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.

Acknowledgments  Thanks to Dennis Shea for Fig. 1. This research is partially sponsored by NASA grant NNX09AH89G.– Kevin E. Trenberth

This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

Perfect storm erupts over new climate data

Jo Chandler 

The Age, March 21, 2012   

See also RealClimate - Updating the CRU and HadCRUT temperature data

THE update of a 160-year-old global temperature record by British scientists, plugging in additional data collected primarily across the Arctic, has resulted in 2010 now being ranked as the warmest year on record, followed by 2005, and bumping the previously top-ranked El Nino super-heated 1998 to third place.

In terms of scientific significance, it's not a big deal, the experts say - ''it makes essentially no difference to the assessment of trends over the last 100 years'', says Dr Blair Trewin, a climatologist at the National Climate Centre of the Bureau of Meteorology. It also falls in line with the other two principle global temperature records - both compiled in the United States.

But in terms of public discussion about climate change, the update has stirred up a disproportionate storm. The peak ranking of 1998 in the British data set was frequently cited by people arguing against the scientific consensus of human-induced global warming as evidence that temperatures had not risen in 14 years.

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The British HadCRUT record is compiled by the British Met Office's Hadley Centre and the Climatic Research Unit at the University of East Anglia. The integrity of the record was caught up in the so-called ''Climategate'' affair in 2009, which circulated hacked emails from CRU scientists. Concerns about the content of the emails provoked at least eight separate inquiries by British and US government agencies, independent panels and universities. None identified wrongdoing by the scientists - although they were criticised for failing to share information - and the science was unassailed.

In some ways - in particular in regard to its approach to extrapolating data over distance - the British record is regarded as the most conservative of the records, Dr Trewin said.

The update draws on additional temperature records to redress ''holes in the [real-time] data over Russia and to an extent Canada. And because the last decade has been particularly warm at high latitudes, that pushes up the overall global averages,'' Dr Trewin said.

''They've also done a much more rigorous job of merging different types of data [from sources including sea-surface buoys as well as ships and satellites] which have all got their own biases and uncertainties.

''As a result, 1998 [which came on the back of a strong El Nino] no longer stands out as being a big outlier in the temperature record, as it was.''

''The inclusion of data from the Arctic gives better global coverage and better agreement with satellite data and other global surface temperature data sets for the observed global warming over the last 30 years and the last decade,'' said Professor David Karoly, a climate expert from the University of Melbourne.

Changes in global temperature estimates in individual years are not statistically significant, he said. But ''the global climate system is still warming and these new data provide additional evidence confirming that''.

The adjustment to the British data will likely later be reflected in the central collated temperature record, maintained by the World Meteorological Organisation, when the full data set is released. It will be publicly available online shortly.

Human cost of inaction incalculable

The Age, OPINION  March 21, 2012 

Ross Gittins, Economics editor.

Do you ever wonder how the environment - the global ecosystem - will cope with the continuing growth in the world population plus the rapid economic development of China, India and various other ''emerging economies''? I do. And it's not a comforting thought.

But now that reputable and highly orthodox outfit the Organisation for Economic Co-operation and Development has attempted to think it through systematically. In its report Environmental Outlook to 2050, it projects existing socio-economic trends for 40 years, assuming no new policies to counter environmental problems.

It's not possible to know what the future holds, of course, and such modelling - economic or scientific - is a highly imperfect way of making predictions. Even so, some idea is better than no idea. It's possible the organisation's projections are unduly pessimistic, but it's just as likely they understate the problem because they don't adequately capture the way various problems could interact and compound.

Then there's the problem of ''tipping points''. We know natural systems have tipping points, beyond which damaging change becomes irreversible. There are likely to be tipping points in climate change, species loss, groundwater depletion and land degradation.

''However, these thresholds are in many cases not yet fully understood, nor are the environmental, social and economic consequences of crossing them,'' the report admits. In which case, they're not allowed for in the projections.

Over the past four decades, human endeavour has unleashed unprecedented economic growth in the pursuit of higher living standards. While the world's population has increased by more than 3 billion people since 1970, the size of the world economy has more than tripled.

Although this growth has pulled millions out of poverty, it has been unevenly distributed and has incurred significant cost to the environment. Natural assets continue to be depleted, with the services those assets deliver already compromised by environmental pollution.

The United Nations is projecting further population growth of 2 billion by 2050. Cities are likely to absorb this growth. By 2050, nearly 70 per cent of the world population is projected to be living in urban areas.

''This will magnify challenges such as air pollution, transport congestion, and the management of waste and water in slums, with serious consequences for human health,'' it says.

The report asks whether the planet's resource base could support ever-increasing demands for energy, food, water and other natural resources, and at the same time absorb our waste streams. Or will the growth process undermine itself?

With all the understatement of a government report we're told that providing for all these extra people and improving the living standards of all will ''challenge our ability to manage and restore those natural assets on which all life depends''.

''Failure to do so will have serious consequences, especially for the poor, and ultimately undermine the growth and human development of future generations.'' Oh. That all?

Without policy action, the world economy in 2050 is projected to be four times bigger than it is today, using about 80 per cent more energy. At the global level the energy mix would be little different from what it is today, with fossil fuels accounting for about 85 per cent, renewables 10 per cent and nuclear 5 per cent.

The emerging economies of Brazil, Russia, India, Indonesia, China and South Africa (the BRIICS) would become major users of fossil fuels. To feed a growing population with changing dietary preferences, agricultural land is projected to expand, leading to a substantial increase in competition for land.

Global emissions of greenhouse gases are projected to increase by half, with most of that coming from energy use. The atmospheric concentration of greenhouse gases could reach almost 685 parts per million, with the global average temperature increasing by 3 to 6 degrees by the end of the century.

''A temperature increase of more than 2 degrees would alter precipitation patterns, increase glacier and permafrost melt, drive sea-level rise, worsen the intensity and frequency of extreme weather events such as heat waves, floods and hurricanes, and become the greatest driver of biodiversity loss,'' the report says.

Loss of biodiversity would continue, especially in Asia, Europe and southern Africa. Native forests would shrink in area by 13 per cent. Commercial forestry would reduce diversity, as would the growing of crops for fuel.

More than 40 per cent of the world's population would be living in water-stressed areas. Environmental flows would be contested, putting ecosystems at risk, and groundwater depletion may become the greatest threat to agriculture and urban water supplies. About 1.4 billion people are projected to still be without basic sanitation.

Urban air pollution would become the top environmental cause of premature death. With growing transport and industrial air emissions, the number of premature deaths linked to airborne particulate matter would more than double to 3.6 million a year, mainly in China and India.

With no policy change, continued degradation and erosion of natural environmental capital could be expected, ''with the risk of irreversible changes that could endanger two centuries of rising living standards''. For openers, the cost of inaction on climate change could lead to a permanent loss of more than 14 per cent in average world consumption per person.

The purpose of reports like this is to motivate rather than depress, of course. The report's implicit assumption is there are policies we could pursue that made population growth and rising material living standards compatible with environmental sustainability.

I hae me doots about that. We're not yet at the point where the sources of official orthodoxy are ready to concede there are limits to economic growth. But this report comes mighty close.