WMO Report: The global climate 2001 – 2010: A decade of climate extremes
World Meteorological Organization Report – A review
This new report from the World Meteorological Society provides a timely summary of measured meteorological trends and extremes, drawn from a wide variety of reliable data sources. The full technical report is both thorough and comprehensive, written principally for professionals in many branches of science, government, commerce and society. This review is a synthesis of the key issues, drawn from both the summary and full technical report. Basically, it’s aimed at people who want to get a reasonably full picture without trawling through the entire 118 pages.
For the public, this report touches on many issues of social, economic and political consequence, and the intention of this review is to highlight the measurable consequences of global warming that we can already perceive, events that cannot reliably be ascribed to global warming, the effects of recent meteorological events on our lives and societies, and the costs already incurred, in both human and financial terms.
The WMO report also affords us an opportunity to consider some of the sceptical arguments that contradict the scientific consensus on anthropogenic climate change, in light of real-world data, coupled with that most perspicacious of facilities, hindsight.
The Report’s Introduction
The following extract positions the report and its findings:
“The first decade of the 21st century was the warmest decade recorded since modern measurements began around 1850. It saw above-average precipitation, including one year – 2010 – that broke all previous records. It was also marked by dramatic climate and weather extremes such as the European heatwave of 2003, the 2010 floods in Pakistan, hurricane Katrina in the United States of America (USA), cyclone Nargis in Myanmar and long-term droughts in the Amazon Basin, Australia and East Africa.
“Many of these events and trends can be explained by the natural variability of the climate system. Rising atmospheric concentrations of greenhouse gases, however, are also affecting the climate. Detecting the respective roles being played by climate variability and human- induced climate change is one of the key challenges facing researchers today”.
1. Climate variability and climate change
Surface temperatures did not increase at the same rate in the last decade as they did in previous decades. The report opens by speculating that natural variation may have played a part in masking surface temperatures:
“The decade 2001–2010 did not experience a major El Niño event, which is normally associated with a warming of the global climate (as occurred for example in the then-record warm year of 1998). La Niña and neutral conditions prevailed until mid-2006, followed by a brief El Niño. Cool La Niña conditions returned from late 2007, a brief El Niño appeared from June 2009 and then a strong La Niña episode started in mid-2010. This short-term natural variability may have masked some of the effects of long-term climate change”.
The report goes on to note that since the 1990s the Arctic Oscillation and North Atlantic Oscillation have “remained mostly in a positive phase, which is associated with warmer and wetter winters in northern and central Europe and the eastern USA, drier winters in the Mediterranean and cold, dry conditions over northern Canada and Greenland”.
The recent cold winters are also addressed: “The winter of 2009/2010, however, saw extremely negative phases with low winter temperatures in northern and central Europe”.
Emissions
The natural cycles are soberly compared to emissions: “Unlike these natural back-and-forth oscillations, human-caused climate change is trending in just one direction”.
While the CO2 figure is well-known, (and has risen to 400ppm in the three years subsequent to the reporting period), the methane figure draws attention; 158% increase over pre-industrial levels. Nitrous oxide has increased the least of all greenhouse gases, at 20% from the same baseline, and the report strikes an optimistic note in regard to ozone emissions reducing sufficiently for the ozone hole to recover ‘in a few decades’.
Table 1. Mixing ratio of carbon dioxide, methane and nitrous oxide in 2010 and the decadal values for 1991–2000 and 2001–2010.
2. The warmest decade
The report is very clear: the warming never stopped.
“The period 2001–2010 was the warmest decade on record since modern meteorological records began around the year 1850. [The global average] is 0.88°C higher than the average temperature of the first decade of the 20th century (1901–1910)”.
“A pronounced increase in the global temperature occurred over the four decades 1971–2010. The global temperature increased at an average estimated rate of 0.17°C per decade during that period, while the trend over the whole period 1880–2010 was only 0.062°C per decade. Furthermore, the increase of 0.21°C in the average decadal temperature from 1991–2000 to 2001–2010 is larger than the increase from 1981–1990 to 1991–2000 (+0.14°C) and larger than for any other two successive decades since the beginning of instrumental records”.
Table 2. Surface temperature anomalies with respect to 1961– 1990: over the globe, northern hemisphere and southern hemisphere for 2001–2010 (A), annual extreme values for 2001–2010 (B) and decadal extreme values for 1881-2010 (C) (source: UK Met Office and US National Oceanic and Atmospheric Administration (NOAA) for global analyses combined; NOAA-National Climate Date Center (NCDC) for the northern and southern hemispheres)
The facts attest to continued warming with a refreshing lack of equivocation: “Nine of the decade’s years were among the 10 warmest on record. The warmest year ever recorded was 2010, with a mean temperature anomaly estimated at 0.54°C above the 14.0°C baseline, followed closely by 2005”.
The report also distinguishes between land and ocean heat, a distinction that sceptics often fail to acknowledge.
“The 2001–2010 decade was also the warmest on record for both land-only and ocean-only surface temperatures. The warmest worldwide land-only surface-air temperature was recorded in 2007, with a temperature anomaly of +0.95°C. The warmest worldwide ocean-only surface temperature was measured in 2003, with an anomaly of +0.4°C above the 1961–1990 average. This is consistent with climate change science, which projects that the ocean surface will warm more slowly than the land because much of the additional heat will be transported down into the ocean depths or lost through evaporation”.
These observations are consistent with recent improvements in the measurement of ocean heat below the 700m limit of pre-existing measurement systems. (Levitus [2012], Nuccitelli [2012] & Balmaseda [2013]).
Figure 1. Decadal global combined surface-air temperature over land and sea-surface temperature (°C) obtained from the average over the three independent datasets maintained by the UK Met Office Hadley Centre and the Climatic Research Unit, University of East Anglia, in the United Kingdom (HadCRU), NOAA-National Climatic Data Center (NCDC) and the US National Aeronautics and Space Administration-Goddard Institute for Space Studies (NASA-GISS). The horizontal grey line indicates the long-term average value for 1961–1990 (14°C).
Regional Data
The report contains detailed information on local responses to climate conditions, as distinct from global averages. Here are a few observations:
- At the national level, a large majority of countries responding to the WMO survey reported that they experienced their warmest decade on record.
- Greenland recorded the world’s largest decadal mean temperature anomaly of +1.71°C.
- Canada recorded the [N.American landmass’] highest anomaly of +1.3°C, making 2001–2010 the country’s warmest decade
- In Australia, the largest country in [Oceania], 2001–2010 was the warmest decade ever, with an anomaly value of +0.48°C.
Usefully, the report also provides a graph of surface temperature anomalies and their relationship to contemporary La Niña and El Niño events:
Figure 2. Annual global surface temperature anomaly for 1950–2010 with reference to the 1961–1990 base period, indicating the years with La Niña events (blue) and those with El Niño events (red) (source: HadCRU, NOAA-NCDC and NASA-GISS)
By way of a conclusion to this section of the report, the WMO make it clear that warming has not stopped in the last decade:
“As shown in Figures 1 and 2, the decade 2001– 2010 continued the upward trend in global temperatures, despite the cooling effects of multiple La Niña episodes and other natural year-to-year variability”.
3. Hot and cold extremes
Many records have been reported in the media during the last decade. The WMO report puts these into context, showing that reported minimum and maximum trends in temperature and precipitation are changing consistently over time. Single day precipitation measurements were also higher than average in the last two decades:
Figure 4. Absolute country records of the daily maximum and minimum temperature and 24-hour total precipitation in the last five decades (source: WMO survey)
“According to the WMO survey, a total of 56 countries (44 per cent) reported their highest absolute daily maximum temperature record over the period 1961–2010 being observed in 2001–2010 compared to 24 per cent in 1991– 2000, with the remaining 32 per cent spread over the earlier three decades. Conversely, 11 per cent (14 out of 127) of the countries reported their absolute daily minimum temperature record being observed in 2001–2010, compared to 32 per cent in 1961–1970 and around 20 per cent in each of the intermediate decades (Figure 4).”
The report notes the number of abnormal heatwave events, and the fatalities incurred, the figures emphasising how extreme heat is far more dangerous than cold:
“Over the course of the 2001–2010 decade, many countries and regions suffered heatwaves…Some of the most dramatic included two severe heatwaves in India in 2002 and 2003, which each killed over 1 000 people; the 2003 summer heatwave over much of Europe, which caused more than 66 000 deaths; and the exceptionally intense and long-lasting heatwave that struck the Russian Federation in July/ August 2010, causing over 55,000 deaths. The WMO survey identifies many other abnormally high-temperature conditions, heatwaves and temperature records around the world”.
“Despite the record average warmth of the decade…the northern hemisphere endured extreme winter conditions from December 2009 to February 2010. Prolonged cold and snow conditions across Europe resulted in over 450 deaths”.
4. Precipitation, floods and droughts
Acknowledging that natural variation in precipitation has always been a feature of our climate, none the less the patterns are changing.
“In all parts of the world, precipitation, floods and droughts vary naturally from year to year and from decade to decade. In addition, because warm air can hold more moisture, it is likely that climate change has influenced the occurrence and intensity of extreme precipitation events”.
Figure 6. Decadal global precipitation anomaly (in mm) relative to the 1961–1990 WMO standard normal (source: NOAA-NCDC )
According to the report:
“The last decade was the wettest decade since 1901, except for the 1950s (Figure 6). In addition, 2010 was the wettest year ever recorded at global level.” Distribution was uneven, however, with Eastern USA for example being “particularly wet”, while at the same time western USA “experienced below-normal precipitation”.
Figure 7. Decadal precipitation anomalies for global land areas for 2001–2010; gridded 1° raingauge-based analysis as normalized departures in mm/year focusing on 1951–2000 base period (source: Global Precipitation ClimatologyCentre (GPCC), Deutscher Wetterdienst, Germany)
The world experienced many precipitation extremes – both excesses and shortages – during the last decade, with floods being the most common:
“According to the WMO survey, floods were the most frequently experienced extreme event over the course of the decade. 20 million people in Asia were affected. However, droughts “affect more people than any other kind of natural disaster owing to their large scale and long-lasting nature. The decade 2001–2010 saw droughts occur in all parts of the world. Some of the highest-impact and long-term droughts struck Australia (in 2002 but also in other years), East Africa (2004 and 2005, resulting in widespread loss of life and food shortages) and the Amazon Basin (2010).”
5. Severe storms
While the number of named storms in the North Atlantic basin exceeded previous averages, elsewhere “the frequency of cyclone activity was generally at average or below-average levels”.
The report notes the deadly effect of extreme storms like Katrina and Nargis, where more than “138 000 people were reported killed or missing, eight million people were affected and thousands of homes were destroyed”. However, no attempt is made to attribute the strength of such storms directly to global warming; elsewhere, the WMO acknowledges the need for better data over longer periods in order to distinguish natural variation from anthropogenic influence.
6. Shrinking ice and rising seas
Once more contradicting claims that global warming has stopped, the WMO report positions the loss of mass, extent and area throughout the cryosphere as a direct result of the increase in temperature, noting the broad, detrimental effects:
“The record warmth of the decade 2001–2010 was accompanied by the melting of ice caps, sea ice and glaciers and the thawing of permafrost. In addition to being a sign of a warming climate, melting ice and snow also affected water supplies, transport routes, infrastructure, marine ecosystems and much more”.
Polar Ice
Already widely reported, the on-going deterioration of Arctic sea-ice is demonstrated in a graphic and a graph showing the dramatic reduction in sea-ice extent and volume (mass balance), with the lowest minimums occurring in the last decade:
Figure 9. Sea-ice extent for September 2007; the magenta line indicates the long-term median from the 1979–2000 base period (left) and Arctic sea-ice extent at the end of the summer melt season from 2007 to 2010 (right) (source: National Snow and Ice Data Center, USA)
The report makes the following observations:
“The five years with the lowest ever recorded sea-ice extent in September were 2005, 2007, 2008, 2009 and 2010. The record minimum extent of 4.28 million km2 – 39 per cent below the long-term average – occurred in 2007 (Figure 9). This record was broken in 2012. The estimated volume of Arctic sea ice has also been declining markedly since 2005, with a new record set in 2010. Meanwhile, Antarctic sea ice has expanded slightly overall, for reasons that continue to be investigated”.
While much attention is given in the media to the extent of Arctic sea-ice – possibly due to the availability of dramatic satellite pictures, the effects of mass loss may be more profound in the long term. Quoting now from the full WMO technical report, the relevance of multi-year ice loss was described:
“The main feature of the sea ice in the Arctic Ocean used to be its stable multi-year character. The continuing observed decline in its volume is the result of both shrinkage of sea-ice cover and a decrease in its average thickness. It is possible to state, therefore, that the decade set the stage for an even more marked future decline in sea-ice extent and volume, ultimately changing the nature of sea ice in the Arctic Ocean from perennial to seasonal”.
Ice Sheets
Considering the importance to sea-level rise in particular, the Greenland and Antarctic ice sheets are given only a single paragraph in the report, perhaps reflecting the uncertainties that still surround the investigations. While the IPCC AR4 (2007) report declined to include estimates of potential ice sheet sea-level rise due to insufficient data, the WMO report notes significant improvements in measurement and monitoring. This is the entirety of the WMO’s discussion of ice sheets, taken from the full technical report:
“At present, there are two major ice sheets which cover most of the Antarctic and Greenland. They contain more than 99 per cent of the planet’s freshwater. During the decade, a significant advance was achieved in the ability to estimate mass balance of the ice sheets using differencing perimeter loss from net accumulation and from satellite gravity measurements. The two techniques are now showing comparable results, leading to the conclusion that there is an acceleration of the net mass loss from the ice sheets (Figure 63*). If this trend continues, ice sheets will contribute to sea-level rise in the 21st century more than any other factor. The first decade of this century can be described as the period in which the trend towards mass loss resulted in consistently negative mass balance for both ice sheets, with the largest losses observed in 2007 and 2008”.
Figure 63 [numbered as per full technical report]. Total ice-sheet mass balance between 1992 and 2009 for (a) Greenland, (b) the Antarctic and (c) the sum of Greenland and the Antarctic in Gt/yr from the Mass Budget Method (solid black circle) and GRACE time variable gravity (solid red triangle) with associated error bars (source: Rignot, 2011)
Glaciers
The world’s glaciers lost more mass in 2001–2010 than in any decade since records began. Snow cover declined significantly in the northern hemisphere (Figures 10 and 11). The temperatures of permafrost (frozen land) areas have been rising, with the 2001–2010 decade marked by an increase in the thickness of the seasonal thaw layer in many northern areas.
The technical report offers a more detailed insight, in particular noting that the World Glacier Monitoring service, which tracks 37 ‘reference’ glaciers, was unequivocal about the loss of glacial ice:
“WGMS refers to the observed melt rate and cumulative loss in glacier thickness as “extraordinary” and states that, based on accumulation area rate data, most of the glaciers are in strong and increasing imbalance with the climate and will continue to melt even without further warming. The cumulative mass loss of the world’s glaciers was larger in the decade 2001–2010 than in any previous decade since records began”.
While the report acknowledges “emerging indications of stability or mass gain in the Karakoram”, it also notes increasing concern over negative mass balance in South American regions and that the Bavarian State Ministry of the Environment and Public Health reported in 2012 that “European glaciers have lost one-third of their volume and half their area since 1850”.
Figure 10. Mean cumulative specific glacier mass balance since 1945/1946 (source: World Glacier Monitoring Service)
Figure 11. Northern hemisphere snow cover anomaly for June (1970–2010) (data source: Rutgers University Global Snow Laboratory, USA). Note: No similar data exist for the southern hemisphere as the land area subject to seasonal snow cover (outside the Antarctic) is very small.
Permafrost and frozen ground
Considering the proximity of major regions of permafrost to the rapidly warming Arctic, it is unsurprising to discover that ground temperatures too are increasing. Of particular concern is the potential for positive feedback if the vast quantities of carbon are released as methane, a greenhouse gas with far greater potential for warming than CO2. According to the WMO report:
“Significant developments in the observing system for permafrost and seasonally frozen ground were achieved during the International Polar Year 2007–2008…the past three decades have seen widespread increases in permafrost temperatures, with colder boreholes warming more rapidly at Alaskan, Canadian and Russian Federation sites. The 2000s are also characterized by an increase in the thickness of the seasonal thaw layer in the northern European part of the Russian Federation, north-eastern Siberia and Chukotka (Russian Federation), Spitsbergen (Norway) and Greenland”.
Effect on Sea Levels
“Global mean sea levels continued to rise over the decade 2001–2010. The observed rate of increase over the decade was about 3 mm/yr year, about double the observed 20th century trend of 1.6 mm/yr. Global sea levels averaged over the decade were about 20 cm higher than those of 1880 (Figure 70). Related to this, it is likely that there has been an increase in coastal high water (IPCC, 2012) owing to anthropogenic influences”.
Figure 70 [numbered as per full technical report]. Global time series of sea-level anomalies (mm) from 1880 to 2010, using tide gauges (blue line, with uncertainty in blue shading) and from 1993 to 2011, using satellite altimetry (red line) (source: Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia: satellite data combined TOPEX/ Poseidon, Jason-1 and Jason-2 (CSIRO), tide gauges (Church and White, 2011)).
Acknowledging that the “rising trend in sea level was consistent over most of the decade, but with some short-term fluctuations, largely the result of ENSO and associated variability in global ocean mass and temperatures”, the report also notes that ESNO cycles have strong effects on spatial distribution: sea-level rise differs from region to region.
The report lists the main contributors to the increase in sea-levels:
“The main contributions to sea-level change in the 20th and 21st centuries are the following:
• Thermal expansion of the oceans (water expands as it warms);
• The addition of mass to the oceans from the melting of glaciers and ice caps in areas such as the Himalayas, Alaska and Patagonia;
• The exchange of mass with the ice sheets of the Antarctic and Greenland;
• The exchange of mass with terrestrial water storages (groundwater, aquifers, dams, lakes).
“Since 1960, the thermal expansion of the oceans and the melting of glaciers and ice caps are the largest contributions to sea-level rise. There has also been an increasing contribution from surface melt from the Greenland ice sheet over this period. These contributions are directly related to recent climate change”.
Finally, the full technical report draws attention to those parts of the world most vulnerable to sea-level increases:
“Millions of people in low-lying nations such as Bangladesh, in the Mekong and other deltas, and Pacific islands such as Tuvalu, will have to respond to rising sea levels during the 21st century and beyond. Improved sea-level rise projections will contribute to more effective coastal planning and management. Adaptation measures include, for example, enhanced building codes, restrictions on where to build and developing infrastructure better able to cope with flooding”.
Curiously, there appears to be what is probably a typographical error in the estimation of potential sea-level rise in the technical report, which states :
“Indications of a larger contribution from the movement of outlet glaciers of both the Greenland and West Antarctic ice sheets have, however, been confirmed in the past decade. If this were a sign of acceleration in response to global warming, it would be a major concern, as the ice sheets contain enough water to raise sea level by 7 m and 6 m, respectively, and any such dynamic response could raise sea level significantly faster than surface melting alone”.
The 7 metre figure is commonly accepted as a value for the Greenland ice sheet, but for the two Antarctic sheets (East and West), the figure should be 61 m).
7. Report Conclusion
The conclusion of the summary report is written with a worthy emphasis on what we don’t know, without positioning the reliable information in a way that projects more damaging potential than has already been demonstrated in the data.
“While climate scientists believe that it is not yet possible to attribute individual extremes to climate change, they increasingly conclude that many recent events would have occurred in a different way – or would not have occurred at all – in the absence of climate change. For example, the likelihood of the 2003 European heatwave occurring was probably substantially increased by rising global temperatures.
“No clear trend has been found in tropical cyclones and extra-tropical storms at the global level. More complete datasets will be needed in order to perform robust analyses of trends in the frequency and intensity of these hazards.
“Distinguishing between natural climate variability and human-induced climate change will also require datasets that are more complete and long-term. A decade is the minimum possible timeframe for detecting temperature changes.
“Assessing trends in extreme weather and climate events requires an even longer timeframe because, by definition, these events do not occur frequently. WMO’s Commission for Climatology is currently addressing new approaches for the improved characterization, assessment and monitoring of these events. In addition, promising new research into the attribution of individual extreme events based on observational and model data is starting to emerge.
“Long-term cryosphere monitoring has emerged as an urgent priority, both for climate research and for understanding the practical implications of the widespread melting. There are still uncertainties with respect to the future evolution of icesheet melting. Understanding cryosphere variability will also help to improve sealevel rise projections, which, in turn, will contribute to more effective coastal planning and management”.
The full technical report conclusion also contain the following acknowledgement of limits to the assessment:
“A great part of the report was dedicated to extremes, covering their impacts on lives and goods and providing through statistics and case studies substantial information on extremes which were recorded worldwide. Disaster-related databases were useful in mapping by disaster event and by region the type and impact of weather and climate extremes. It is still not yet possible to make a definite link between the increase in the observed losses with an increase in the frequency and intensity of extreme events. Other factors come into play, such as increased vulnerability and exposure of populations and the increase in the number of reports of disasters. Nevertheless, it is worthwhile to note a large increase of loss of life from heat conditions, particularly in two unprecedented extreme heatwaves that affected Europe in summer 2003 and the Russian Federation in summer 2010”.
And there was, in fact, some good news:
“On the other hand, there were fewer death due to storms and floods in 2001–2010 compared with 1991–2000 figures, with a decrease of 16 per cent and 43 per cent, respectively. This is an encouraging indicator of the importance of weather warning systems against extreme meteorological and hydrological events which continuously improved over the decade”.
The Final Word
Predictably, for a report grounded in factual data, the World Meteorological Organisation ends its report with calls for better monitoring, more coherent and longer-term data, and a deeper understanding that only better information can provide.
The report has, for many scientists and observers, confirmed much of what was already found in evidence and models. It has proved a useful interim measure of many aspects of global warming, and the climate change it catalyses. There are no overt political messages, nor advice, just an emphasis on the value of reliable information when so much may be at stake, so profound the consequences of failure to address the issue of climate change while we have time.
The report does not paint a picture of gross global catastrophe, nor attempt attribution to the suffering already endured where the data does not support such assertions. It does make clear that climate change may already be contributing to many deaths and much hardship, and by implication, that many more may be expected in a future in which emissions are not bought under control.
Yet there must also be hope, for while the predations of climate change that have already occurred are to be deplored, they are no so great in number that we might assume time has run out. All climate change assessments are probabilistic; this report strengthens the mainstream scientific and societal assessments of future impacts, but it does not yet seem it is too late to avoid impacts of such an extent that they might destabilise our entire global civilisation.
Graham Wayne, July 2013
Small Epiphanies 