Missed Greenland melt cause raises sea level concern

A team of scientists (the tiny figures in the foreground) at the southwest margin of the Greenland Ice Sheet. Almost all of the surface of the sheet melted in July 2012 - and there's a lot more ice benath the surface, that's why faster melting could be so serious for sea level rise. Credit: University of Sheffield

A team of scientists (the tiny figures in the foreground) at the southwest margin of the Greenland Ice Sheet. Almost all of the surface of the sheet melted in July 2012 – and there’s a lot more ice benath the surface, that’s why faster melting could be so serious for sea level rise. Credit: University of Sheffield

The almost complete melting of Greenland’s ice sheet surface on July 11-12 2012 was caused by climate processes not projected by models. That’s according to an international team led by Edward Hanna from the University of Sheffield, UK that has looked at what might have driven the melt. “The models used to predict future climate change are clearly deficient in simulating some of the recent jet stream changes that we have shown to be responsible for enhanced warming and ice melt over Greenland,” Edward told me. And the world needs to pay attention when Greenland defrosts, as the water it produces is a major part of sea level rise.

Having long studied the Greenland ice sheet, or GrIS, Edward was perhaps one of the people least amazed by 2012’s events. “Last year’s record melt was a bit of a surprise, but perhaps not so startling in retrospect, given strong recent warming of the ice sheet area since the early-mid 1990s,” he said. With other scientists he has also found a clear change since 2007 in early summer Arctic wind patterns relative to previous decades that has led to warm Greenland summers. In particular, jet stream patterns of winds weaving north and south in drunken circles around the pole have changed to drive warm winds over Greenland. That study also linked these changes to cool, wet summers in the UK since 2007, whose unusual wetness in 2012 is seemingly the other face of the GrIS melt coin. Read the rest of this entry »

Worse extreme temperature effects urge farming precautions

Stanford University's Sharon Gourdji talks about her study on increasing extreme heat during sensitive crop flowering periods. Credit: IOP Publishing, via Creative Commons license, see citation below.

Since 1980, maize and wheat crops in many places have been increasingly exposed to extreme heat during sensitive flowering phases that can damage them and cause harvests to fail. That’s according to scientists at Stanford University, California, who predict that this problem will increase for these crops, and also hit rice. In fact, the area of maize and rice hit by such deadly heat is set to expand more quickly through to the 2050s. “Crop breeders need to think carefully about how to incorporate heat tolerance, particularly during the flowering period, into wheat, maize and rice,” Stanford’s Sharon Gourdji told me.

Our warming climate affects farming in many ways. For example higher temperatures, and the higher CO2 levels that are primarily responsible for them, can speed up the photosynthesis process that makes plants grow. Meanwhile, shifting rainfall patterns are set to have serious impacts on important farming areas. In 2011, Sharon’s teammate David Lobell and other scientists showed that overall crop production growth worldwide has been held back by such changes in the last three decades. But they didn’t discuss how environmental changes might influence future food availability.

“The net impact of all these factors is the golden question, but notoriously difficult to model,” Sharon explained. “Also, the most relevant of these factors, and the associated adaptation measures, differ by location and crop. Therefore most modelling studies to date look at net impacts on just a given region, or type of cropping system.” To make worldwide predictions that could help secure our future food supply, Sharon’s team had to concentrate on a smaller, simpler issue. “We focused on extreme heat during flowering,” Sharon said. “This is one aspect of global environmental change that could be particularly risky for crops regardless of other more gradual changes that are taking place simultaneously.”

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Deciphering climate messages via the heart of the atom

Vemork Hydroelectric Plant at Rjukan, Norway, which Hans Suess advised on heavy water production, telling Nazi Germany it couldn't make heavy water quickly enough for military use. His expertise with heavy water was part of an interest in nuclear science that led him to become a pioneer in carbon dating.

Vemork Hydroelectric Plant at Rjukan, Norway, which Hans Suess advised on heavy water production, telling Nazi Germany it couldn’t make heavy water quickly enough for military use. His expertise with heavy water was part of an interest in nuclear science that led him to become a pioneer in carbon dating.

When Hans Suess chose to study physical chemistry, he went nuclear, apparently overturning two generations of family tradition. Hans was born in 1909, just as his father Franz succeeded his grandfather Eduard as a geology professor at the University of Vienna. Hans got his PhD from the same university in 1936, but in studying heavy water he was set to aid the historic advances in nuclear science of the time. Yet a transatlantic scientific coincidence would bring him back to more environmental science, and see him help pioneer radiocarbon measurements. With that expertise, Hans showed humans were raising atmospheric CO2 levels, and revealed another surprising source of variations in climate.

The common theme to these achievements was how neutrons and protons combine in an atom’s nucleus. For example, hydrogen atoms found in conventional water have just a single proton in their nuclei. In heavy water, some of these atoms are replaced by a rarer form of hydrogen, known as deuterium, whose atoms have an extra neutron in their nuclei. That gives heavy water properties that can help nuclear reactors, which Nazi Germany notoriously hoped to exploit to make nuclear weapons.

With Hitler’s armies occupying Austria just two years after Hans finished his PhD, his expertise brought him to the attention of the Nazi regime. They called him in to advise a hydroelectric power plant in Vemork, Norway, that was making heavy water. Hans visited several times, reporting that it couldn’t make heavy water quickly enough for military use. Allied forces destroyed it in 1943 anyway, in audacious raids fictionalised in the film “Heroes of Telemark”.

Alongside working with heavy water, Hans studied why the chemical elements exist in the amounts that they do. The answer laid in how stable different numbers of protons and neutrons are when they come together in nuclei. He continued this work after the Second World War in West Germany, helping develop the “Nuclear Shell Theory” explanation, which other scientists won the Nobel Prize for Physics for in 1963. Suess missed out on this acclaim partly because two teams came up with the explanation at the same time. But when the other team, based at the University of Chicago, invited him to visit, Hans’ life changed course towards unravelling the secrets of Earth’s history. Read the rest of this entry »

Historical sea voyage sends manmade warming signal

The HMS Challenger sailed 69,000 miles, taking around 360 temperature soundings on the first global marine expedition from 1873-1876. This painting, by William Frederick Mitchell, is from  its earlier life as a warship, in 1858.

The HMS Challenger sailed 69,000 miles, taking around 360 temperature soundings on the first global marine expedition from 1873-1876. This painting, by William Frederick Mitchell, is from its earlier life as a warship, in 1858.

Data from a 19th century scientific mission, the first global marine research expedition, have provided strong evidence that humans have influenced climate throughout the entire 20th century. From 1873–1876 the HMS Challenger, a corvette of the British Royal Navy, sailed 69,000 miles and took hundreds of ocean temperature soundings. Last year, scientists used its measurements to show the top 700 metres of the ocean has warmed around 0.33°C since Challenger’s voyage. Understandably, seeing a global effect in the limited Challenger data is fraught with difficulty. Nevertheless, Will Hobbs from the University of Tasmania, Australia, and Joshua Willis at NASA’s Jet Propulsion Laboratory in Pasadena, California, have now checked if this warming is linked to humans. “Even accounting for all uncertainties and limitations, the temperature change could not be realistically explained by natural variability alone, implying a long-term human signal,” Will told me.

Having swapped cannons for labs, among HMS Challenger’s projects was a series of around 360 soundings for temperature. At each sounding, its scientists dropped pressure-protected thermometers into the ocean attached to a rope every 100 fathoms (182 m) down to 1000 fathoms depth. “The scientists kept detailed records of how each measurement was taken, problems encountered, and how accurate and precise their measurements were,” Will said. “All instruments were calibrated in a lab before and after the expedition. So we have a lot of information about what level of accuracy we can expect, in some ways more than from modern automated observing systems, which are usually left to their own devices after deployment.” Read the rest of this entry »

Lifting the fog of war and climate

FIDO (Fog Investigation Dispersal Operations) petrol burners are ignited on either side of the main runway at Graveley, Huntingdonshire, as an Avro Lancaster of No. 35 Squadron RAF takes off in deteriorating weather, 28 May 1945.Guy Callendar helped devise the FIDO system.

FIDO (Fog Investigation Dispersal Operations) petrol burners are ignited on either side of the main runway at Graveley, Huntingdonshire, as an Avro Lancaster of No. 35 Squadron RAF takes off in deteriorating weather, 28 May 1945. Guy Callendar helped devise the FIDO system.

  • This is part two of a two-part post. Read part one here.

In November 1943, the British Royal Air Force used a new secret weapon in anger for the first time. Called FIDO, or Fog Investigation and Dispersal Operation, it was a system of petrol burners that cleared fogbound airfields by raising their temperatures several degrees. It let the Allies launch and land warplanes safely when their enemies were still grounded by poor visibility. Newspapers billed it as near miraculous, crediting it with shortening the war and saving the lives of 10,000 airmen. But for one of the engineers behind it, Guy Callendar, it was just another way to combine his interest in weather and climate with his heat expertise.

From 1922-1941 Guy had worked on the Callendar Steam Tables, which he filled with data to help other engineers and scientists working with steam equipment. But after a decade carefully measuring the interaction between temperature, pressure and other properties in steam, his thoughts turned increasingly to climate. By 1938 he had stood up in front of a room of sceptical meteorologists, telling them that the world was warming, and burning fossil fuels was the cause. And while that marked a key turning point in identifying and understanding global warming, his later work in collecting evidence for that argument may have been still more important.

With his CO2 theory getting a frosty reception, and with his steam work winding down, Guy scoured scientific papers for evidence to back his argument. Since scientists like Svante Arrhenius had first suggested an important role for CO2 in climate in the 19th century and even earlier, physics had made some important advances. Earlier scientists knew that gases like CO2 absorbed infrared radiation but in the 1920s they made leaps forward in understanding why.

The frequency of the wave of infrared radiation, the number of oscillations it goes through per second, matches motions in the gas molecules that absorb it. For example, if the molecules spin at a similar frequency to the radiation’s oscillations, they can absorb the its energy. Also, atoms such as oxygen and carbon in the molecule can move, pushed by thermal energy and pulled by chemical bonds between them. That creates a vibration, and if the frequency of the vibration matches that of the infrared radiation, the vibration can absorb the radiation’s energy Read the rest of this entry »