As of three years ago the Earth was already committed to rise of global mean temperatures by 2.4°C. This is the shocking conclusion of a new study in the journal Proceedings of the National Academy of Sciences (PNAS).
This is highly significant since the Intergovernmental Panel on Climate Change (IPCC) has already warned that a rise in global temperature in the range of 1 to 3°C will lead to catastrophic consequences, including “widespread loss of biodiversity, widespread deglaciation of the Greenland Ice Sheet, and a major reduction of area and volume of Hindu-Kush-Himalaya-Tibetan glaciers. These systems provide the head-waters for most major river systems of Asia.”
These glaciers, predicted to continue their rapid retreat in the next few decades, provide food and water to over two billion people. Their fate and the fate of billions of people are bound together.
The EU has also set as its absolute policy target efforts to prevent global mean temperature increases reaching the ‘red line’ of 2° C, the point beyond which the entire global climate system is in imminent risk of unravelling, with consequences that beggar imagining.
Glaciers in the Bhutan-Himalaya. Glacial lakes have been rapidly forming on the surface of the debris-covered glaciers in this region during the last few decades. Due to unique conditions in the Arctic (which is heating much faster than global averages) mean temperatures must be doubled to show what is going on there.
With a committed rise of nearly 5°C (9°F), the already diminishing sea-ice will continue to abate at alarming rates and the Greenland Ice Sheet may begin to crumble under climatic pressures. The researchers estimate the long-term exposure (thousands of years) of the Greenland Ice Sheet to a minimum warming between 1.9–4.6°C will lead to a complete melt of Greenland. Such a melt would raise sea levels by seven meters (23 feet).
The authors warn that time is running out. Unless tough mitigation policies on greenhouse gases are put in place, they say the Earth will be locked into a rise of 3°C by 2030. They write that “CO2 mitigation polices are extremely critical if we want to limit further increases in the committed warming.”
One question sceptics often ask is, “if things are really that bad, how come the planet hasn’t yet yet felt the full force of climate change?” So far, Earth has experienced a mean warming of 0.76°C since the late 1800s. The true effects of climate change are being masked by other factors, the most important of which is air pollution.
Some types of air pollution send aerosols that reflect light like a mirror, brightening the planet and thereby cooling it. The pollutants’ effect in masking rising temperatures has been estimated at as high as 47%. However, as countries clean up their skies, the masking effects of such pollutants is suddenly removed, causing the Earth to undergo dramatic warming. This relationship between dwindling air pollutants and higher temperatures can already be seen in Europe, whose skies have largely been cleared of major industrial pollutants.
Air pollution is itself a health and environmental threat, so the researchers do not suggest that countries should abandon efforts to clean it up, but they do say we need to be aware of the likely additional rise in temperature such clean-ups will likely trigger.
The researchers argue that better models are needed to provide nations with more accurate predications of the relationship between air pollutants and greenhouse gases. “This is not easy and the costs may be substantial for developing such models and the associated observing systems, but,” the scientists conclude, “we do not have much choice.”
A sobering reminder of the scale of the challenge we now confront came yesterday from the director of the World Wildlife Fund in Scotland. “Apart from all-out nuclear war or an asteroid hitting the planet, there isn’t anything bigger than climate change”, was Dr Richard Dixon’s blunt assessment. “If you don’t tackle climate change, the global economy will fall apart. If you don’t tackle climate change the natural resources we rely on from timber to fish stocks will also be severely disrupted”.
Dixon’s concern is that economic crises such as the credit crunch and the banking crisis are serving as a dangerous distraction from the overwhelming threat posed by climate collapse.