Warming weakens deep freeze on Arctic islands

Pictures from William D'Andrea's August 2012 expedition to Svalbard. There are 24 slides in this series - apologies for the poor formatting. Credit: The Earth Institute/Columbia University

Normally 6°C wouldn’t be very warm – but in the Norwegian islands of Svalbard it’s a sultry modern summer, unlike anything seen for at least 1,800 years. That’s what sediments taken from an Arctic lake have told William D’Andrea from Columbia University in New York and a US team. It’s even warmer than a medieval warm period when parts of the northern half of the planet were as hot as, or hotter, than today. And while the record they’ve made reflects just this one site, it adds to the picture showing how unique today’s climate is. It’s also another step towards understanding how climate has changed through history, William told me.

Climate dynamics are extremely complex, and cooling in some locations can happen at the same time as warming in others, or increased precipitation in some places along with drought in other places,” he said. “These are the fingerprints we are trying to map and understand by generating such reconstructions.”

The fingerprints slowly become clearer as scientists collect more historical records, often as tubes of ice drilled from glaciers, or of mud and rock drilled from sea and lake beds. The tubes, or cores, cut through layers of mud or ice built up year after year. Scientists can then use fossils and chemicals to date and work out what conditions were like when they were laid down.

Economy-CO2 link reveals GDP weakness

The key US National Oceanic and Atmospheric Administration (NOAA) site where CO2 concentrations in the air are monitored, at Mauna Loa, Hawaii. Unlike CO2 emissions, these CO2 concentrations can be readily measured directly, so Edward Ionides, José Tapia Granados, and Óscar Carpintero used them to study their link with global GDP. Credit NOAA

Researchers have confirmed a relationship that is making climate change tough to fight: economic growth and atmospheric CO2 concentrations have been tightly linked for the past 50 years. That’s what the University of Michigan‘s Edward Ionides and co-workers found by looking at levels of the greenhouse gas and gross domestic product (GDP), an important measure of countries’ financial performance, at a worldwide level. “GDP growth is like a proxy for CO2 concentration growth,” Edward told Simple Climate. “Under business-as-usual conditions, these two quantities are measuring essentially the same thing. This highlights a problem with using GDP as a measure of progress.”

Until now, much research on the link between CO2 and economic growth has looked at figures for each country. Some think using each country’s CO2 emissions separately “should be more informative”, Edward said. But there are problems with recording emissions accurately, plus goods or services used in one country often result in CO2 emissions in another. So, with Michigan colleague José Tapia Granados, and Óscar Carpintero from the University of Valladolid, Spain, Ionides went to the worldwide level for “a new and simpler perspective”.

As well as the total of all countries’ GDP, they used precisely measured atmospheric CO2 levels, rather than the more uncertain emission figures. “In addition, concentration of CO2, rather than the level of emissions, is the variable directly determining the global climate,” Óscar said. “Change in the atmospheric concentration is the result of emissions – mainly from burning fossil fuels, since natural emissions from volcanoes are estimated as a tiny fraction of man-made emissions – minus removals by natural sinks.”

Atmospheric CO2 (monthly average) as measured in air samples collected at Mauna Loa, Hawaii from Feburary 1958 to Februrary 2012. Units are parts per million by volume. Estimated preindustrial concentrations, at levels between 200 and 300 ppm, would be far out of the graph. The graph is often known as the Keeling curve. Credit: University of Michigan

Volcano cloud over tree-ring temperatures clears

Pennsylvania State University’s Michael Mann thinks he has found the reason behind key outstanding disagreements between the historical temperature record based on tree rings and climate models for the same period. Credit: Pennylvania State University

The sudden chills violent volcano eruptions cast over the world centuries ago effectively erased themselves from the historical climate record produced by examining tree-rings. So suggests a team led by Michael Mann from Pennsylvania State University, who famously used 1,000 years of tree-ring measurements in the “hockey stick” graph showing how unusual today’s temperatures are. Michael warns the skipped years could affect scientists’ estimates of how much the world warms in response to greenhouse gases in the atmosphere, known as its climate sensitivity. But other than the volcano years, the scientist notes that tree-ring data is a remarkably accurate match with the climate models they used for comparison. “Interestingly, the effect has little influence on long-term trends, including conclusions about how previous temperatures compares to modern ones,” he told me. “Instead, it appears only to have implications for how strong past short-term cooling events were.”

A tree’s age can usually be told from the rings that form across its trunk representing each year’s growth. How thick each ring is shows how much the tree grew in the year in question, which is influenced by the temperatures that tree experienced. That means examining the thickness of rings in old trees can provide a way to tell temperatures back through history. Many challenges have already been overcome in turning this simple-sounding idea into a history of the world’s temperature, but Michael was still troubled by one particular detail.

Fighting sea rise with mirrors and mock volcanoes

To fight sea level rise it might take pumping suphur dioxide emissions into the atmosphere equivalent to 1991's Mount Pinatubo eruption (shown here) every 18 months. Credit: USGS/Cascades Volcano Observatory

If CO2 emissions can’t be cut, simulating volcanoes could help the 150 million people across the world threatened by rising sea levels, scientists said this week. But the UK, Denmark and China-based researchers who reach these conclusions also warn such ‘geo-engineering’ measures could be dangerous in other ways. “Substituting geo-engineering for greenhouse gas emission control would be to burden future generations with enormous risk,” said Svetlana Jevrejeva of the UK’s National Oceanography Centre.

150 million people worldwide are thought to live within 1 metre of high tide, Jevrejeva’s team notes. In 2007, the Intergovernmental Panel on Climate Change (IPCC) estimated that by 2100 the sea level would rise by 0.18–0.59 metres. However, since then several researchers have suggested a rise of 1-1.5 metres would be more likely.