Fact check: has global warming paused?

● By Dr. Andrew Glikson, Australian National University ● “The UN’s climate change chief, Rajendra Pachauri, has acknowledged a 17-year pause in global temperature rises, confirmed recently by Britain’s Met Office, but said it would need to last ‘30 to 40 years at least’ to break the long-term global warming trend.” – The Australian, Feb 22 2013 Since the onset of the industrial age (from 1750 AD) Earth’s atmosphere, surface and ocean temperatures have warmed. This is mainly due to the rise in greenhouse gases (CO2, CH4, N2O, O3, halocarbons, stratospheric water vapour from CH4) by a total of +3.06 Watt/m2. Other drivers include black carbon (+0.1 Watt/m2) and solar irradiance – the latter during the first half of the 20th century (+0.12 Watt/m2). Warming was in part mitigated by emitted sulphur aerosols (direct effects -0.5 Watt/m2; cloud albedo effects -0.7 Watt/m2) and by land clearing (-0.2 Watt/m2). Cyclic, regional and transient climate effects are related to the ENSO cycle, water vapour (whose concentration depends on air temperature) and volcanic events. The fastest warming occurs in the polar regions: this is where there is the biggest albedo (or reflectiveness) contrast between ice and water, and where little or no water vapour exists in the atmosphere. The consequent warming trend, as measured by NASA, NOAA and Hadley-Met and analysed by Berkeley (see Figure 1), indicates a rise in average land temperature by about +1.5°C over the past 250 years, and about +0.9°C in the past 50 years. A sharp rise in temperatures from about 1975-1976 was related to both an accelerated rise in CO2 and a decrease in emission of SO2 from coal and oil due to clean air policies (see Figure 2). Cleaner air decreases the reflectiveness of the atmosphere, thus driving further warming ...Zum vollständigen Artikel

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