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news watch ‘Unequivocal’ global warming What are the media saying? Journalists have been asking important questions. What has changed since 2007? This is the first time the IPCC has given explicit warning that the world cannot continue burning fossil fuels at the same rate. In one respect, the news has improved. The 2007 assessment forecast that a doubling of GHG would lead to at least a 2ºC rise in temperature. Its refined models now suggest 1.5ºC. What can be done? Simon Oakes looks at the evidence in the latest IPCC report T he Intergovernmental Panel on Climate Change (IPCC) has published its fifth assessment report in 23 years (the last was in 2007). The IPCC is a small organisation, based in Geneva. Its reports, many thousands of pages in length, draw on the work of over 800 scientists and hundreds of peer-reviewed scientific papers. The 2013 assessment states that it is ‘virtually certain’ humans are to blame for ‘unequivocal’ global warming. Key findings of the report Temperature anomaly (°C) Map showing global temperature anomalies over the 5 years from 2006 to 2010. Dark red shows areas that were warmer than average and dark blue areas that were colder than average 0.6 0.4 0.2 0 2002 −0.2 Lago Argentino −0.4 Figure 1 Global temperature anomaly, 1850–2010. The graph shows a range for each decade, compared with the average for 1961–90 Global average surface temperature change (°C) Temperature Sea level 1.0 6 4 Highest scenario Lowest scenario Range 2 Range 0 −1 1950 Source: IPCC 2000 2050 2100 Year 0.8 Highest scenario Lowest scenario Range 0.6 A NASA photograph from 2 October 2013 showing retreat of the Upsala Glacier in Argentina, compared to observations in earlier years Range 0.4 0.2 Isn’t the evidence unreliable? Not really. As one journalist recently pointed out: ‘Arctic sea ice is melting. That is not a view or an opinion. It is a visible measurable fact’. The IPCC states that although global warming appears to have ‘slowed down’ since 1998, that was an exceptionally hot El Niño year, which may have influenced earlier projections. The role of oceans, which have absorbed more than 90% of warming so far, is not fully understood. Recent extreme weather that contradicts IPCC predictions (such as wet summers and cold winters in the UK) does not disprove global warming. Most places will have more hot and fewer cold temperature extremes, but there will still be anomalies. Upsala Glacier Further reading Read more on certainty: www.tinyurl.com/pkub6ua See the actual IPCC projections: www.tinyurl.com/qadtvud Guardian briefings at www.tinyurl.com/pjb9dsf and www.tinyurl.com/ k7p93ny Certainty and science In science little is ‘certain’ and much is complex. This sits uneasily with a mass media based on headline ‘facts’. As a geographer you need to understand what geographic projections really mean. For instance, in 2007 the IPCC thought it ‘very likely’ that anthropogenic GHGs were the main cause of global warming. The 2013 assessment says it is ‘extremely likely’. Technically, this means the IPCC is now 95–100% certain (a 1:20 chance the projections are wrong). The 2007 assessment was 90–100% certain (giving a higher 1:10 possibility of error). BBC report: www.bbc.co.uk/news/science-environment-24292615 Source: IPCC 0 2000 2020 2040 2060 2080 2100 Year Figure 2 IPCC projections for temperature and sea level under two different scenarios 20 2013 −0.6 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Global average sea-level rise (metres) Atmospheric concentrations of the greenhouse gases (GHGs) carbon dioxide, methane and nitrous oxide are at levels ‘unprecedented in at least the last 800,000 years’. ■ Since 1750 fossil-fuel burning has increased the carbon in the Earth’s atmosphere by about 40%. ■ More than half of all global warming since 1951 is attributed to human activity (Figure 1). ■ Sea level has risen by 20 cm since 1900. ■ Mean global temperature is now 0.85ºC higher than in 1880 (Figure 1). ■ In the twenty-first century the sea level will rise another 26–82 cm and the temperature will go up 0.3–4.8ºC (Figure 2). ■ By 2100, global temperature is ‘likely’ to have risen by more than 1.5ºC relative to 1850. ■ It is ‘virtually certain’ that the upper 700 m of the ocean has warmed since 1971. Major ice sheets have lost mass, land-based glaciers continue to shrink and Artic sea-ice cover has fallen since 1979. The IPCC is ‘virtually certain’ of further permafrost melting. ■ Up to 40% of anthropogenic carbon dioxide will remain in the atmosphere more than 1,000 years, so it is ‘virtually certain’ that warming will continue beyond 2100, potentially beyond the threshold needed for Greenland’s ice sheet to melt (bringing a 7m sea level rise). ■ Dangerous and unpredictable changes are projected unless warming is limited to 2ºC. This means only another 15–25 years of global GHG emissions, and requires an immediate, collective and unlikely shift in all nations’ energy policies. On an optimistic note, the UK’s Lord Stern notes in one newspaper that: • the UK Climate Change Act of 2008 promises significant mitigation (by committing the UK to reduce its annual emissions by at least 80% by 2050, compared with 1990) • the costs of solar photovoltaics and other technologies are falling • Barack Obama and China’s Xi Jinping have pledged to collaborate to tackle climate change Geography Review If global warming is a conspiracy, it is ‘surely the most remarkable conspiracy in history, and the only one backed by a crushing majority of peer-reviewed scientific papers’ according to Harry Eyres: www.tinyurl. com/qaozc28 February 2014 GeographyReviewExtras You can download a pdf of this spread from our website to print as a poster. See back cover. Simon Oakes 21