11 December 2015, The Conversation, Climate and the rise and fall of civilizations: a lesson from the past. 2015 will likely be the hottest year on record, beating the previous record set only in 2014. It is also likely to be the first year the global average temperature reaches 1℃ above pre-industrial temperatures (measured from 1880-1899). Global warming is raising temperatures, and this year’s El Niño has pushed temperatures higher still. Although 2015 is unusually hot, 1℃ symbolically marks the halfway point to 2℃, widely considered to be the threshold of “dangerous” climate change. In fact an additional 0.5-1℃ is actually masked by sulphur aerosols which we have added to the atmosphere alongside greenhouse gases. A temperature level of 1℃ (above pre-industrial levels) is similar to or warmer than the peak temperatures of the early Holocene epoch approximately 8,000-7,200 years ago. Studies of the early Holocene provide clues to what was such a world like. The climate roller-coaster The last ice age (or Last Glacial Maximum) peaked around 26,000 years ago. The earth warmed over the coming millennia, driven by an increase in radiation from the sun due to changes in the earth’s orbit (the Milankovic cycles) amplified by CO₂ released from warming water, which further warmed the atmosphere. But even as the earth warmed it was interrupted by cooler periods known as “stadials”. These were caused by melt water from melting ice sheets which cool large regions of the ocean. Marked climate variability and extreme weather events during the early Holocene retarded development of sustainable agriculture. Sparse human settlements existed about 12,000 – 11,000 years ago. The flourishing of human civilisation from about 10,000 years ago, and in particular from 7,000 years ago, critically depended on stabilisation of climate conditions which allowed planting and harvesting of seed and growing of crops, facilitating growth of villages and towns and thereby of civilisation. Read More here
Category Archives: The Science
10 December 2015, The VERB, The 1.5 Placebo.Moments before the Paris climate agreement is to be decided upon, the draft text (as of 3pm Wednesday) still contains three different options surrounding its overall objective. The draft retains options to limit warming to below 2°C, below 1.5°C, or ‘well’ below 2°C with mention of scaling up efforts to stay below 1.5°C. As The Verb reported earlier in the week, half a degree of difference is highly economically significant, and for vulnerable nations may be the difference between persistence and functional destruction. For many small island states, a target of 1.5°C has been a long held objective that has gained increasing support in Paris. “To hold the temperature within 2°C is not an acceptable goal,” said Barbados Environment Minister Dr. Denis Lowe, who argued that “the goal should be 1.5°C, that is what will keep us alive.” Day one of the negotiations saw leaders of 106 states sign a statement calling for 1.5°C to become the long-term temperature goal. This was in lieu of the 2°C target, established in the 2009 Copenhagen meeting. Canada, France, Germany, the UK, Australia, China, and the US have since expressed support for including the 1.5°C target in some capacity. At first glance, this shift sounds good – it may even make people feel better about the possibility of avoiding the worst impacts of climate change. But it appears to be a placebo, and it may come at the expense of more effective responses. The challenge of limiting warming to below 1.5°C is enormous given current carbon dioxide concentrations and emissions. Some call it unfeasible. There are currently 400 parts per million of carbon dioxide in the atmosphere, a number that is growing at two parts per million per year. New research suggests that we would have to stabilise concentrations between 420 and 440 parts per million by 2100 to have even a 50% chance of holding warming below 1.5°C. Read More here
16 November 2015, Science Daily, Earth’s climate more sensitive to carbon dioxide than previously thought. Ancient climates on Earth may have been more sensitive to carbon dioxide than was previously thought, according to new research from Binghamton University. A team of Binghamton University researchers including geology PhD student Elliot A. Jagniecki and professors Tim Lowenstein, David Jenkins and Robert Demicco examined nahcolite crystals found in Colorado’s Green River Formation, formed 50 million years old during a hothouse climate. They found that CO2 levels during this time may have been as low as 680 parts per million (ppm), nearly half the 1,125 ppm predicted by previous experiments. The new data suggests that past predictions significantly underestimate the impact of greenhouse warming and that Earth’s climate may be more sensitive to increased carbon dioxide than was once thought, said Lowenstein. “The significance of this is that CO2 50 million years ago may not have been as high as we once thought it was, but the climate back then was significantly warmer than it is today,” said Lowenstein. CO2 levels in the atmosphere today have reached 400 ppm. According to current projections, doubling the CO2 will result in a rise in the global average temperature of 3 degrees Centigrade. This new research suggests that the effects of CO2 on global warming may be underestimated. “Take notice that carbon dioxide 50 million years ago may not have been as high as we once thought it was. We may reach that level in the next century, and so the climate change from that increase could be pretty severe, pretty dramatic. CO2 and other climate forcings may be more important for global warming than we realized.” The only direct measurement of carbon dioxide is from ice cores, which only go back less than 1 million years. Lowenstein and his team are trying to develop ways to estimate ancient carbon dioxide in the atmosphere using indirect proxies. He said that their approach is different than any ever undertaken. “These are direct chemical measurements that are based on equilibrium thermodynamics,” he said. “These are direct laboratory experiments, so I think they’re really reliable. Read More here
10 November 2015, Science Daily, Geophysics could slow Antarctic ice retreat. Gravitational effects, variations in Earth structure could damp rise in global sea levels. The anticipated melting of the massive West Antarctic Ice Sheet could be slowed by two big factors that are largely overlooked in current computer models, according to a new study. The findings, published online in Nature Communications, suggest that the impact on global sea levels from the retreating ice sheet could be less drastic — or at least more gradual — than recent computer simulations have indicated. Over the past year, numerous studies have warned that parts of the West Antarctic Ice Sheet are on the verge of a runaway retreat. Just last week a high-profile research paper forecast that this could lead eventually to a rise in global sea levels of as much as three metres. The authors of the new Nature Communications paper, however, focus on two geophysical elements that they say aren’t adequately reflected in computer simulations for this region: the surprisingly powerful gravitational pull of the immense ice sheet on surrounding water, and the unusually fluid nature of the mantle beneath the bedrock that the ice sits on. “The fate of the polar ice sheets in a warming world is a major concern for policy makers — and attention is rightly focused on the importance of restraining CO2 emissions and preparing for rising sea levels,” says lead author Natalya Gomez, an assistant professor of Earth and Planetary Sciences at McGill University in Montreal. “But our study shows that for Antarctica, in particular, computer models also need to take into account how gravitational effects and variations in Earth structure could affect the pace of future ice-sheet loss.” Read More here