How lessons from space put the greenhouse effect on the front page

Normally during a total lunar eclipse, like this one on April 15, 2014, you can still see the moon, but in 1963 Normally during a total lunar eclipse, like this one on April 15, 2014, you can still see the moon, but in 1963

Normally during a total lunar eclipse, like this one on April 15, 2014, you can still see the moon, but in 1963 Jim Hansen saw it disappear completely. Explaining why would send him on a scientific journey to Venus, before coming back down to Earth. Image credit: NASA

Jim Hansen’s life changed on the evening the moon disappeared completely. In a building in a cornfield Jim and fellow University of Iowa students Andy Lacis and John Zink, and their professor Satoshi Matsushima, peered in surprise through a small telescope into the wintry sky. It was December 1963, and they had seen the moon replaced by a black, starless circle during a lunar eclipse. The moon always passes into Earth’s shadow during such eclipses, but usually you can still see it.

At first they were confused, but then they remembered that in March there had been a big volcanic eruption. Mount Agung in Indonesia had thrown tonnes of dust and chemicals into the air: perhaps that was blocking out the little light they’d normally have seen? With a spectrometer attached to their telescope they measured the moon’s brightness, data Jim would then base his first scientific research on. Using this record to work out the amount of ‘sulphate aerosol’ particles needed to make the moon disappear, Jim began a lifelong interest in planets’ atmospheres. That would lead him to become director of the NASA Goddard Institute of Space Studies (GISS), where he has led the way in exposing the threat from human CO2 emissions.

Jim was born in Iowa in 1941, the fifth of seven children of a farmer, who had left school at 14, and his wife. As he grew up they moved into the town of Denison, his father becoming a bartender and his mother a waitress, and Jim spending his time playing pool and basketball. Jim claims he wasn’t academic, but found maths and science the easiest subjects, always getting the best grades in them in his school. Though his parents divorced when he was young, public college wasn’t expensive at the time, meaning Jim could save enough money to go to the University of Iowa.

The university had an especially strong astronomy department, headed by James Van Allen, after whom brackets of space surrounding the Earth are named. These ‘Van Allen Belts’ are layers of particles that he discovered, held in place by the planet’s magnetic field. Satoshi Matsushima, a member of Van Allen’s department, could see Jim and Andy’s potential and convinced them to take exams to qualify for PhD degrees a year early. Both passed, with Jim getting one of the highest scores, and were offered NASA funding that covered all their costs.

A few months later, it was Satoshi who suggested measuring the eclipse’s brightness, feeding Jim’s interest in atmospheres on other planets. “Observing the lunar eclipse in 1963 forced me to think about aerosols in our atmosphere,” Jim told me. “That led to thinking about Venus aerosols.” In an undergraduate seminar course Jim had given a talk about the atmospheres of outer planets, which James Van Allen had attended. The elder scientist told him that recently measured data was suggesting Venus’ surface was very hot. Aerosols stopped light reaching the Earth during the eclipse – could they be warming up Venus by stopping heat escaping, Jim wondered? That would become the subject of his PhD, and Satoshi and James Van Allen would be his advisors. Read the rest of this entry »

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Real-world grounding could cool 21st century outlook

The world's surface air temperature change ("anomaly"), relative to the world's mean temperature of 58° F or 14.5° C, averaged over land and oceans from 1975 to 2008. Inset are two periods of no warming or cooling within this overall warming trend. Copyright 2009 American Geophysical Union. Reproduced/modified by permission of American Geophysical Union.

The world’s surface air temperature change (“anomaly”), relative to the world’s mean temperature of 58° F or 14.5° C, averaged over land and oceans from 1975 to 2008. Inset are two periods of no warming or cooling within this overall warming trend. Copyright 2009 American Geophysical Union. Reproduced/modified by permission of Wiley/American Geophysical Union, see citation below.

Starting climate models from measured data helps simulate the early-2000s global warming hiatus better, and reduces projections for warming through to 2035. Jerry Meehl and Haiyan Teng have compared such ‘initialised’ model runs against more common ‘uninitialised’ ones starting without real-life conditions. The scientists, from the US National Centre for Atmospheric Research (NCAR) in Boulder, Colorado, find initialised runs get closer to modelling that hiatus and surprisingly rapid warming in the 1970s. Using the same approach, admittedly rough 30-year predictions for Earth’s surface air temperature initialised in 2006 are about one-sixth less than uninitialised projections. “We have evidence that if we would have had this methodology in the 1990s, we could have predicted the early-2000s hiatus,” Jerry told me.

The hiatus Jerry and Haiyan studied – an easing off in the rate of global warming since 1998 – is perhaps the aspect of climate change most hotly debated today. But hiatus is a slippery word, whose meaning depends on who is highlighting what points on which graph. Climate skeptics will often infer that it’s evidence that global warming is not a problem, or that it shows we know too little to act on climate change. The UN Intergovernmental Panel on Climate Change puts it in plain numbers: the rate of warming from 1998-2012 was 0.05°C per decade; from 1951 to 2012, it was 0.12°C per decade. “In addition to robust multi-decadal warming, global mean surface temperature exhibits substantial decadal and interannual variability,” it adds.  “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.”

In a paper published online in the journal Geophysical Research Letters last week, Jerry and Haiyan touch on the current best explanations of the let-up. These include the chilling effect of recent volcano eruptions, but mostly focus on cooling in the Pacific as part of a natural cycle. Called the Interdecadal Pacific Oscillation (IPO), this regular wobble in sea surface temperatures has likely partly masked greenhouse-gas driven warming. The IPO has also been linked to a larger warming than might have been expected from greenhouse gases alone in the 1970s, the NCAR researchers add. Read the rest of this entry »

Enhanced fingerprinting strengthens evidence for human warming role

Microwave sounding units, like the AMSU units on the Aqua satellite, shown here, can be used to take temperature measurements from different layers in the atmosphere. Ben Santer and his colleagues use this information to find a 'fingerprint' of human impact on recent climate changes. Credit: NASA

Microwave sounding units, like the AMSU units on the Aqua satellite, shown here, can be used to take temperature measurements from different layers in the atmosphere. Ben Santer and his colleagues use this information to find a ‘fingerprint’ of human impact on recent climate changes. Credit: NASA

We have left a clear climate change ‘fingerprint’ in the atmosphere, through CO2 emissions that have made air near the Earth’s surface warmer and caused cooling higher up. That’s according to Ben Santer from Lawrence Livermore National Laboratory (LLNL) in California, who started studying this fingerprint in the mid-1990s, and his expert team. They have strengthened the case by comparing satellite-recorded temperature data against the latest climate models including natural variations within Earth’s climate system, and from the sun and volcanic eruptions. Ben hopes that in the process their results will finally answer ill-tempered criticism his earlier work attracted, and lingering doubts over what causes global warming.

“There are folks out there even today that posit that the entire observed surface warming since 1950 is due to a slight uptick in the Sun’s energy output,” Ben told me. “That’s a testable hypothesis.  In this paper we look at whether changes in the sun plausibly explain the observed changes that we’ve monitored from space since 1979. The very clear answer is that they cannot. Natural influences alone, the sun, volcanoes, internal variability, either individually or in combination, cannot explain this very distinctive pattern of warming.”

That pattern emerged when scientists in the 1960s did some of the first computer modelling experiments looking at what would happen on an Earth with higher CO2 levels in the air. “They got back this very curious warming in the lower atmosphere and cooling of the upper levels of the atmosphere,” Ben explained. The effect happens because most of the gas molecules in the atmosphere, including CO2, sit relatively near to Earth’s surface. CO2’s greenhouse effect lets heat energy from the Sun reach the Earth, but interrupts some of it getting back to the upper atmosphere and outer space. Adding more CO2 by burning fossil fuels therefore warms the lower atmosphere, or troposphere, and cools the stratosphere, 6-30 miles above the Earth’s surface.  Read the rest of this entry »

Continuing the fight for CO2 monitoring

  • This is part two of a two-part post. Read part one here.
Dave Keeling had to balance his work measuring CO2's rise in the air and tracking its movements through the Earth's systems with fighting to get the money to fund his work. Credit: Scripps Institution of Oceanography

Dave Keeling had to balance his work measuring CO2’s rise in the air and tracking its movements through the Earth’s systems with fighting to get the money to fund his work. Credit: Scripps Institution of Oceanography

By 1963, having directly measured a steady increase in CO2 levels over five years, Dave Keeling felt he had clearly shown the value of such non-stop monitoring. But that message hadn’t reached government decision makers. And so Dave swung into the first battle in the war to continue tracking the key greenhouse gas that has flared up repeatedly in the following decades.

Thanks to four new instruments called spectrophotometers, Dave had been able to use the same molecular movements that allow CO2 to absorb heat to measure it. Though his most famous site was at Mauna Loa in Hawaii, one was also installed in Antarctica. Another sailed on a ship and the final one stayed at Dave’s lab at Scripps Institution of Oceanography analysing samples collected in vacuum-filled five litre flasks from aircraft and elsewhere. Thanks to funds from 1957-1958’s International Geophysical Year a team of scientists was busy collecting a “snapshot” of CO2 data that Dave’s boss at Scripps, Roger Revelle, wanted.

So in 1961, Dave moved his family to Sweden for a year to work out exactly what the measurements were showing. He took a fellowship at the Meteorological Institute, University of Stockholm working with its new director Bert Bolin, who had earlier worked on the first computerised weather forecast. With measurements ongoing, annual ‘breathing’ cycles of rising and falling CO2 and the increasing trend underlying them became ever clearer.

Together, Dave and Bert found CO2 concentrations were going up by 0.06 ppm per month on average. Bert also undertook a series of complex calculations by hand to work out CO2 movement and cycles in its levels. In doing so he was showing how oceans, plants on land, and human fossil fuel burning contributed to the patterns that would later need computer models for fuller analysis. This, Dave felt, clearly showed why non-stop CO2 monitoring was needed rather than just snapshots. But by 1963 the shipboard spectrophotometer had come home, and Dave had also called back the one in Antarctica. And with funding cuts biting at the Weather Bureau, now part of the National Oceanic and Atmospheric Administration (NOAA), the staff at Mauna Loa fell from eight to three. And soon afterwards, a problem with Dave’s equipment proved too much for the overstretched team to fix.

“Suddenly there were no precise measurements being made of atmospheric CO2 anywhere,” he recalled. “I had seen the budget cut coming early in 1963 and had tried to prevent its terminating the CO2 program at Mauna Loa Observatory. I even went to Washington to plead for supplemental funding. This had no tangible effect, however, until the cessation of measurements actually occurred. The National Science Foundation (NSF) then found funds to pay for an additional technician at Mauna Loa. I learned a lesson that environmental time-series programs have no particular priority in the funding world, even if their main value lies in maintaining long-term continuity of measurements.” Read the rest of this entry »

Diving deep into ocean data uncovers ‘missing heat’ treasure

A new ocean reanalysis called ORAS4, here showing the difference between September 2012 sea temperatures and the average for 1989-2009 (not part of the latest study), has helped show that extra heat trapped in the atmosphere by CO2 humans are emitting is buried in the deep ocean. Credit: ECMWF

A new ocean reanalysis called ORAS4, here showing the difference between September 2012 sea temperatures and the average for 1989-2009 (not part of the latest study), has helped show that extra heat trapped in the atmosphere by CO2 humans are emitting is buried in the deep ocean. Credit: ECMWF

A newly-made picture of ocean history has backed a theory that the missing piece of a climate puzzle at the edge of space lies deep in Earth’s waters. The puzzle comes because the amount of heat energy our planet has absorbed should have warmed it more than it seems to have done. But now, using an ocean reanalysis assembled from data gathered from many sources, UK and US researchers have shown especially strong recent warming in oceans below 700m. “We have found some energy buried at depths,” Kevin Trenberth from the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. “We also have a plausible explanation for it related to changes in winds.”

In 2010, Kevin went public over his worries about a budget that didn’t balance. But rather than money, that budget tallies heat energy from the Sun entering the top of the atmosphere against energy the Earth radiates back out into space. Satellite measurements show more energy coming in than leaving, which is what causes global warming. But Kevin noticed that existing measurements showed the world hadn’t warmed as much since 2003 as this budget would suggest.

With over nine-tenths of the surplus energy coming into the Earth going into the sea, the deep ocean has always looked the likeliest hiding place for the missing heat. However, temperature data from those depths is scarce, making the theory hard to prove. Yet, in the years since Kevin pointed out the problem, scientists have gathered some clues to back that explanation. For example, some used a model that includes the complex links between the atmosphere, land, oceans, and sea ice to run five simulations of the 21st century. They found warming slowdowns on the Earth’s surface similar to what has happened in the 2000s, with the heat going into the deep oceans. But even this just underlined the importance of using measurements to see the effect directly. Read the rest of this entry »

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

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

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

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