Tag Archives: global warming

Four degrees and beyond – new research highlights dangers of runaway climate change

Posted on by
Reply
Transactions of the Royal Society A - The Four Degree World

The Four Degree World

ABC SCIENCE: A collection of papers published last week (Philosophical Transactions Of The Royal Society A) examine the impact global warming may have on weather patterns, food production and population by the end of this century.

Since the late 1990s, many researchers and policy makers have held a 2°C global temperature increase relative to pre-industrial times as a benchmark limit for global warming, saying that keeping warming below this threshold increases the likelihood that catastrophic changes can be avoided.

But it appears we are unlikely to meet that target, say researchers, and an average global warming of 4°C by the end of this century is more likely.

A study by Richard Betts (Hadley Centre) suggests that a 4°C rise relative to pre-industrial levels could happen by the 2070s, if emissions are high, if the temperature response to those emissions is high, and if the feedback cycles to those emissions are high.

If we reach 4°C higher by the 2070s, it would put us on track for an almost 7°C increase by the end of the century, he says. The projections are too uncertain to say exactly what trajectory we are on, says Betts.

“I don’t particularly sign up to the fact that 2°C is some kind of threshold for catastrophic climate change,” he says. “It’s all about risk assessment. The greater the warming, the larger the impact. The faster the warming, the harder it is to adapt to any impact. The risk becomes greater the more you put into the system.”

Read More

ABC Science story

Philosophical Transactions Of The Royal Society A – original articles, many free access.

Share

Sea Level Rise to Be Higher & Faster Than Predicted by IPCC

Posted on by

Recent research suggests that global warming-related sea level rise will be faster and greater than previously forecast. The poles are experiencing disproportionate warming and are undergoing accelerated melting. The amount of this melt will largely determine the degree of sea-level rise over coming centuries.

Polar Ice Is Melting Faster Than Predicted

Polar Ice Is Melting Faster Than Predicted

Melting is proceeding at an unprecedented pace that already exceeds the worst-case scenario in the 2007 IPCC report, and there is a growing scientific consensus that the IPCC wildly underestimated the rapidity and extent of glacial melting.

Over the coming centuries anthropogenic warming will be the main driver of sea-level rise, even if emissions decreased and atmospheric levels of CO2 stabilised at 450ppm. If we burn all remaining fossil fuel stores then sea level will be over 10 metres higher than it is today.

While the single biggest contributor to sea-level rise during the twentieth century was the melting of non-polar glaciers (such as those in the Himalayas and Andes), polar ice is predicted to rapidly overtake it. Thermal expansion of the oceans will also play a role but will pale into insignificance compared to the amount of water currently locked up in Greenland and Antarctica (which will raise sea level by 70 metres if it all melts).

Rising Sea Levels Are Due To Global Warming-Induced Climate CHange

Rising Sea Levels Are Due To Global Warming-Induced Climate Change

There are three main mechanisms contributing to the accelerating loss of polar ice.

Glacial lubrication by meltwater (where melting freshwater infiltrates through cracks in the glacier, reaching the bedrock and acting as a lubricant that accelerates glacial flow) is one mechanism. Initially thought to be the most important mechanism, it is probably not the primary factor that will lead to accelerated sea level rise.

A second mechanism is the break-up of floating ice shelves (like the Antarctic’s Larsen B shelf). While not increasing sea level directly (because they are already floating), they appear to act as a “cork” for the glacier behind them. Once they disappear, glacial flow accelerates significantly – This was observed at Larsen B where immediate glacial acceleration (of eight times normal speed) followed its demise.

The third (and probably most important) mechanism of ice loss has only just been discovered – the melting of Antarctic ice by the upwelling of warmer water from several hundred metres below the surface of the sea. This is occurring in increasingly greater amounts due to global warming. A warming pole has changed the pattern of wind flow around Antarctica, in turn changing sea currents and directing warm water towards vulnerable ice shelves.

This process is already happening to some ice shelves (notably the ice shelf holding back the massive Pine Island glacier) and could cause a sea-level rise of 3.3 metres over the next few hundred years.

Antarcticas Ice Is Disappearing

Antarctica's Ice Is Disappearing

Summary: Ice at the poles is melting much faster than predicted, and the majority of sea level experts are expecting at least a metre of sea-level rise by 2100.

Paul Roth is a health professional concerned about human-caused global warming and climate change. He is the founder of Climate Change Health, a blog dedicated to documenting climate change and its effects on human health.

Article Source: http://EzineArticles.com/?expert=Paul_Andrew_Roth
http://EzineArticles.com/?Sea-Level-Rise-to-Be-Higher-and-Faster-Than-Predicted-by-IPCC&id=2663108

Share

MIT predicts warming of 5.2 degress by 2100

Posted on by
Reply

The most comprehensive modeling yet carried out on the likelihood of how much hotter the Earth’s climate will get in this century shows that without rapid and massive action, the problem will be about twice as severe as previously estimated six years ago – and could be even worse than that.

The study uses the MIT Integrated Global Systems Model, a detailed computer simulation of global economic activity and climate processes that has been developed and refined by the Joint Program on the Science and Policy of Global Change since the early 1990s. The new research involved 400 runs of the model with each run using slight variations in input parameters, selected so that each run has about an equal probability of being correct based on present observations and knowledge. Other research groups have estimated the probabilities of various outcomes, based on variations in the physical response of the climate system itself. But the MIT model is the only one that interactively includes detailed treatment of possible changes in human activities as well – such as the degree of economic growth, with its associated energy use, in different countries.

Study co-author Ronald Prinn, the co-director of the Joint Program and director of MIT’s Center for Global Change Science, says that, regarding global warming, it is important “to base our opinions and policies on the peer-reviewed science,” he says. And in the peer-reviewed literature, the MIT model, unlike any other, looks in great detail at the effects of economic activity coupled with the effects of atmospheric, oceanic and biological systems. “In that sense, our work is unique,” he says.

The new projections, published this month in the American Meteorological Society’s Journal of Climate, indicate a median probability of surface warming of 5.2 degrees Celsius by 2100, with a 90% probability range of 3.5 to 7.4 degrees. This can be compared to a median projected increase in the 2003 study of just 2.4 degrees.

Share