Ok, maybe not the sky itself… but the clouds. According to recent research by climate scientists in New Zealand, global cloud heights have dropped.
Researchers at The University of Auckland have reported a decreasing trend in average global cloud heights from 2000 to 2010, based on data gathered by the Multi-angle Imaging SpectroRadiometer (MISR) on NASA’s Terra satellite. The change over the ten-year span was 30 to 40 meters (about 100 to 130 feet), and was mostly due to fewer clouds at higher altitudes.
It’s suspected that this may be indicative of some sort of atmospheric cooling mechanism in play that could help counteract global warming.
“This is the first time we have been able to accurately measure changes in global cloud height and, while the record is too short to be definitive, it provides just a hint that something quite important might be going on,” said lead researcher Professor Roger Davies.
A steady reduction in cloud heights could help the planet radiate heat into space, thus serving as a negative feedback in the global warming process. The exact cause of the drop in cloud altitude is not yet known, but it could reasonably be resulting from a change in circulation patterns that otherwise form high-altitude clouds.
Cloud heights are just one of the many factors that affect climate, and until now have not been able to be measured globally over a long span of time.
“Clouds are one of the biggest uncertainties in our ability to predict future climate,” said Davies. “Cloud height is extremely difficult to model and therefore hasn’t been considered in models of future climate. For the first time we have been able to accurately measure the height of clouds on a global basis, and the challenge now will be to incorporate that information into climate models. It will provide a check on how well the models are doing, and may ultimately lead to better ones.”
While Terra data showed yearly variations in global cloud heights, the most extreme caused by El Niño and La Niña events in the Pacific, the overall trend for the years measured was a decrease.
Continuing research will be needed to determine future trends and how they may impact warming.
“If cloud heights come back up in the next ten years we would conclude that they are not slowing climate change,” Davies said. “But if they keep coming down it will be very significant.”
The team’s study was recently published in the journal Geophysical Research Letters.
Terra is a multi-national, multi-disciplinary mission involving partnerships with the aerospace agencies of Canada and Japan. An important part of NASA’s Science Mission, Terra is helping scientists around the world better understand and protect our home planet.
It’s been said many times that the most Earthlike world in our solar system is not a planet at all, but rather Saturn’s moon Titan. At first it may not seem obvious why; being only a bit larger than the planet Mercury and coated in a thick opaque atmosphere containing methane and hydrocarbons, Titan sure doesn’t look like our home planet. But once it’s realized that this is the only moon known to even have a substantial atmosphere, and that atmosphere creates a hydrologic cycle on its surface that mimics Earth’s – complete with weather, rain, and gully-carving streams that feed liquid methane into enormous lakes – the similarities become more evident. Which, of course, is precisely why Titan continues to hold such fascination for scientists.
Now, researchers have identified yet another similarity between Saturn’s hazy moon and our own planet: Titan’s energy budget is in equilibrium, making it much more like Earth than the gas giant it orbits.
A team of researchers led by Liming Li of the Department of Earth and Atmospheric Sciences at the University of Houston in Texas has completed the first-ever investigation of the energy balance of Titan, using data acquired by telescopes and the Cassini spacecraft from 2004 to 2010.
Energy balance (or “budget”) refers to the radiation a planet or moon receives from the Sun versus what it puts out. Saturn, Jupiter and Neptune emit more energy than they receive, which indicates an internal energy source. Earth radiates about the same amount as it receives, so it is said to be in equilibrium… similar to what is now shown to be the case for Titan.
The energy absorption and reflection rates of a planet’s – or moon’s! – atmosphere are important clues to the state of its climate and weather. Different balances of energy or changes in those balances can indicate climate change – global cooling or global warming, for instance.
Of course, this doesn’t mean Titan is a balmy world. At nearly 300 degrees below zero (F) it has an environment that even the most extreme Earth-based life would find inhospitable. Although Titan’s atmosphere is ten times thicker than Earth’s its composition is very different, permitting easy passage of infrared radiation (a.k.a. “heat”) and thus exhibits an “anti-greenhouse” effect, unlike Earth or, on the opposite end of the scale, Venus.
Still, some stable process is in place on Saturn’s moon that allows for distribution of solar energy across its surface, within its atmosphere and back out into space. With results due in from Cassini from a flyby on Jan. 2, perhaps there will soon be even more clues as to what that may be.
The team’s report was published in the AGU’s Geophysical Research Letters on December 15, 2011. Li, L., et al. (2011), The global energy balance of Titan, Geophys. Res. Lett., 38, L23201, doi:10.1029/2011GL050053.
The body of evidence for climate change is strong and convincing, and multiple lines of evidence show the changes are caused largely by human activities. The consensus among scientists about the reality of the phenomenon is also convincing.
But from the nature of public discussions on the subject today – at least in the US – that consensus might not be apparent. And somehow the discussion has become a “debate,” which is often divided down political party lines.
“We have to make it clear that the ice sheets are not Republicans or Democrats – they don’t have a political agenda as they disappear,” said Michael Mann, a physicist at Pennsylvania State University, who has been at the recent forefront of climate research. “Certain facts cannot be denied. We have to find a way to steer the conversation to a good faith debate about what we can do about the problem, not this bad faith debate about the reality of it.”
Mann referred specifically to an infamous memo sent out by GOP political consultant Frank Luntz in 2002 to President George Bush, “which basically said that if the public comes to understand the reality of this problem they will demand policy action to deal with it,” Mann said, “and so you need to manufacture doubt and controversy and uncertainty and cultivate a set of scientists who can act for advocates essentially for fossil fuel industry. And that is what is happened.”
And the science became politicized. “If you can politicize something in today’s political environment,” Mann continued, “you can immediately get half the population on your side. Unfortunately the forces of anti-science — those who deny the science — have been very effective in politicizing the framing.”
But thousands of scientists from almost 200 countries around the world agreed on the most recent Intergovernmental Panel on Climate Change (IPCC) report which said most of the observed increases in global average temperatures is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Additionally, the US National Academy of Sciences, the National Academies of all the G-8 nations, the American Association for the Advancement of Science and several other scientific bodies have all issued equivalent statements of consensus of the reality of human-caused climate change.
“Certain facts cannot be denied because you don’t like the implications,” Mann said.
Mann is probably best known for known for his “hockey stick” reconstruction of past climate, (Nature, 1998) which shows the world is warmer now than it has been for at least 1000 years. The “hockey stick” has been attacked by climate change deniers, and while new research has better defined the data, it has not been disproven, nor is it the only line of evidence for global warming.
“The hockey stick is not ‘the’ pillar of evidence for the reality of climate change,” Mann said. “There are multiple pillars that include just the basic understanding of chemistry and physics. But it is one of the more visually compelling pieces of evidence for warming.”
Mann conceded that various other studies and reconstructions of past climate data don’t agree entirely and that there are uncertainties of how much warming will continue because the predictions are based on models, which attempt to predict the future.
“There are legitimate uncertainties, but unfortunately the public discourse is so far removed from where the scientific discourse and controversies actually are, “Mann said. “There is not an uncertainty of the reality of climate change, that sea levels are going to rise, that arctic sea ice will be gone in a few decades or a whole lot of other areas, but we do have an uncertainty in our ability to project regional climate change.”
Mann said scientists don’t completely understand the El Nino and La Nina affects, how cloud feedback will influence the warming and other modeling issues.
However, Mann said, the science has improved over the past few years, and still, there is enough evidence for not just a hockey stick, but an entire hockey league.
“Every reconstruction reveals that the warming is indeed anomalous in a very long term context. Global temperatures are running the highest they have ever run. The twelve month running averages are warmer than they have ever been in documented history. There is no cooling of the globe and no decline to hide,” Mann said referring to the “Climategate” emails that were stolen from East Anglia climate research center and leaked just a few weeks before the Copenhagen climate summit in late 2009.
“Hackers stole thousands of emails –private correspondences between scientists,” said Mann, “and their words were cherry picked, taken out of context and distorted to make it sound like scientists were engaged in some sort of hoax.”
‘Hide the decline’ actually meant the scientists were going to remove unreliable tree-ring data, not cover up any decline in temperatures.
Mann said the real crime was the illegal theft of private correspondence, in addition to the moral crime of intentionally distorting what scientists believe and think.
Mann took his audience to task by saying, “I’d like to say the mainstream media recognized the manufactured controversy for what is was, but they didn’t, entirely.” He also admitted that scientists have not done all they could in the past to make the science clear and their words convincing.
But looking at the current political climate, Mann asked for journalists’ help in the future.
“No doubt we are in for a period of months or even years where climate science is likely to be subject to the sort of politically motivated inquisition that we haven’t seen, frankly, since the 1950’s,” he said. “It is necessary and important for the scientific community to do the best it I can to defend itself from this oncoming attack, and frankly, we are entirely reliant on the willingness of the mainstream media to serve in its role as the critical and independent arbiter and not just report the two sides of the so-called debate, but to actually establish what is fact and what is fiction. The scientists will not be successful against the attack that is coming unless the media is serving its role.”
Mann ended his talk with a picture of his daughter enthralled by a polar bear at a zoo. “I don’t want to have to tell my daughter that polar bears became extinct because we failed to counter a well funded effort to distract the public,” he said.
Note: For any reader who thinks they need to leave a comment to debate the climate change science, before posting, please take a look at the following information:
A new NASA report says the past decade was the warmest ever on Earth, at least since modern temperature measurements began in 1880. The study analyzed global surface temperatures and also found that 2009 was the second-warmest year on record, again since modern temperature measurements began. Last year was only a small fraction of a degree cooler than 2005, the warmest yet, putting 2009 in a virtual tie with the other hottest years, which have all occurred since 1998. This annual surface temperature study is one that always generates considerable interest — and some controversy. Gavin Schmidt, a climatologist at NASA’s Goddard Institute for Space Studies (GISS) offered some context on this latest report, in an interview with the NASA Earth Science News Team.
NASA’s Earth Science News Team: Every year, some of the same questions come up about the temperature record. What are they?
Gavin Schmidt: First, do the annual rankings mean anything? Second, how should we interpret all of the changes from year to year — or inter-annual variability — the ups and downs that occur in the record over short time periods? Third, why does NASA GISS get a slightly different answer than the Met Office Hadley Centre does? Fourth, is GISS somehow cooking the books in its handling and analysis of the data?
NASA: 2009 just came in as tied as the 2nd warmest on record, which seems notable. What is the significance of the yearly temperature rankings?
Gavin Schmidt: In fact, for any individual year, the ranking isn’t particularly meaningful. The difference between the second warmest and sixth warmest years, for example, is trivial. The media is always interested in the annual rankings, but whether it’s 2003, 2007, or 2009 that’s second warmest doesn’t really mean much because the difference between the years is so small. The rankings are more meaningful as you look at longer averages and decade-long trends.
NASA: Why does GISS get a different answer than the Met Office Hadley Centre [a UK climate research group that works jointly with the Climatic Research Unit at the University of East Anglia to perform an analysis of global temperatures]?
Gavin Schmidt: It’s mainly related to the way the weather station data is extrapolated. The Hadley Centre uses basically the same data sets as GISS, for example, but it doesn’t fill in large areas of the Arctic and Antarctic regions where fixed monitoring stations don’t exist. Instead of leaving those areas out from our analysis, you can use numbers from the nearest available stations, as long as they are within 1,200 kilometers. Overall, this gives the GISS product more complete coverage of the polar areas.
NASA: Some might hear the word “extrapolate” and conclude that you’re “making up” data. How would you reply to such criticism?
Gavin Schmidt: The assumption is simply that the Arctic Ocean as a whole is warming at the average of the stations around it. What people forget is that if you don’t put any values in for the areas where stations are sparse, then when you go to calculate the global mean, you’re actually assuming that the Arctic is warming at the same rate as the global mean. So, either way you are making an assumption.
Which one of those is the better assumption? Given all the changes we’ve observed in the Arctic sea ice with satellites, we believe it’s better to assume the Arctic Ocean is changing at the same rate as the other stations around the Arctic. That’s given GISS a slightly larger warming, particularly in the last couple of years, relative to the Hadley Centre.
NASA: Many have noted that the winter has been particularly cold and snowy in some parts of the United States and elsewhere. Does this mean that climate change isn’t happening?
Gavin Schmidt: No, it doesn’t, though you can’t dismiss people’s concerns and questions about the fact that local temperatures have been cool. Just remember that there’s always going to be variability. That’s weather. As a result, some areas will still have occasionally cool temperatures — even record-breaking cool — as average temperatures are expected to continue to rise globally.
NASA: So what’s happening in the United States may be quite different than what’s happening in other areas of the world?
Gavin Schmidt: Yes, especially for short time periods. Keep in mind that that the contiguous United States represents just 1.5 percent of Earth’s surface.
NASA: GISS has been accused by critics of manipulating data. Has this changed the way that GISS handles its temperature data?
Gavin Schmidt: Indeed, there are people who believe that GISS uses its own private data or somehow massages the data to get the answer we want. That’s completely inaccurate. We do an analysis of the publicly available data that is collected by other groups. All of the data is available to the public for download, as are the computer programs used to analyze it. One of the reasons the GISS numbers are used and quoted so widely by scientists is that the process is completely open to outside scrutiny.
NASA: What about the meteorological stations? There have been suggestions that some of the stations are located in the wrong place, are using outdated instrumentation, etc.
Gavin Schmidt: Global weather services gather far more data than we need. To get the structure of the monthly or yearly anomalies over the United States, for example, you’d just need a handful of stations, but there are actually some 1,100 of them. You could throw out 50 percent of the station data or more, and you’d get basically the same answers. Individual stations do get old and break down, since they’re exposed to the elements, but this is just one of things that the NOAA has to deal with. One recent innovation is the set up of a climate reference network alongside the current stations so that they can look for potentially serious issues at the large scale – and they haven’t found any yet.
[/caption]There are different gases in the atmosphere. There’s nitrogen (the most abundant of them all), oxygen, and argon. There are of course a lot more but they’re no more than 1% of the entire atmosphere.
Among the minority are the greenhouse gases, carbon dioxide being the most prominent of them all. These gases are presently cast as harmful to the planet, being the primary cause of global warming. Of course, they’re only harmful because they’ve exceeded their ideal levels. Anything that comes in excess is not good, right?
At ideal levels, greenhouse gases play an important role in keeping our planet warm enough for us and other organisms to live comfortably. Unfortunately, the rapid rate of industrialization has caused greenhouse gases to accumulate, forming a layer too thick for infrared radiation (which originally came in from the Sun as solar radiation) to escape.
The different gases in the atmosphere actually make up five principal layers. Starting from the lowest layer, there’s the Troposphere, followed by Stratosphere, then the Mesosphere, then Thermosphere, and finally the Exosphere.
The peak of Mount Everest, high as it is, is still part of the Troposphere. The Stratosphere is the layer at which most weather balloons fly. The Mesosphere is where meteors mostly ignite. The Thermosphere is where the International Space Station orbits.
Since the Karman line (which serves as the boundary between the Earth’s immediate atmosphere and outer space) is found in the lower region of the Thermosphere, much of this layer of gases in the atmosphere is considered outer space. Finally, the exosphere, being the outermost layer, is where you can find the lightest gases: hydrogen and helium.
Many properties of the gases in the atmosphere are dependent on the altitude at which they are found. For instance, average density of these gases generally decrease as one rises to higher altitudes. As a result, the pressure (being due to the collisions of the particles that make up the gas) also decreases in the same manner.
Since the force of gravity pulls down on the masses of these gases, the heavier gases are typically found near the surface of the Earth while the lightest ones (e.g. hydrogen and helium) are found in higher altitudes. All these properties are just generalizations though. Temperature and fluid dynamics also influence these properties.
Ice cores and deep sea bed cores provide the best available record of changes in global temperature and CO2 content of the atmosphere going back 800,000 years. The data shows a clear periodicity in global temperatures which is thought to be linked to the Milankovitch cycle.
Back in 1920, Milutin Milankovitch, a Serbian mathematician, proposed that fine changes in Earth’s orbit around the Sun could explain an approximately 100,000 year cycle in glaciation seen from geological evidence. The tilt of the Earth’s axis swings slightly over a 41,000 year cycle – the eccentricity of Earth’s orbit moves from almost circular to more elliptical and back again over a 413,000 year cycle – and overlaying that you have not only the precession of the equinoxes, which is an inherent wobble in the Earth’s axial spin over a 26,000 year cycle, but also a precession of the whole of Earth’s orbit over a 23,000 year cycle.
Ice core data does show a rough concordance between glaciation and the synchronicity of these orbital cycles. Even though there’s no significant change in the mean amount of solar radiation reaching the Earth over the period of its annual orbit – the orbital changes can lead to increased polar shadowing and cooling.
Once ice does start advancing from the poles, a positive feedback loop can develop – since more ice increases the albedo of Earth’s surface and reflects more of the Sun’s heat back into space, thus reducing mean global temperatures.
It’s thought that what limits the ice advancing is increasing CO2 in the atmosphere – which can be measured from trapped bubbles of air in the ice cores. More ice formation leads to less exposed land area for photosynthesis and silicate rock weathering to remove CO2 from the atmosphere. So the more ice that’s formed, the more CO2 accumulates in the atmosphere – which causes mean global temperatures to rise, which limits ongoing ice formation.
Of course the opposite is true in an ice-melting phase. Ice melting also follows a positive feedback loop since less ice means less albedo, meaning less solar radiation is reflected back into space and mean global temperatures rise. But again, CO2 becomes the limiting factor. With more exposed land, more CO2 is drawn from the atmosphere by photosynthesizing forests and rock weathering. A consequent drop in atmospheric CO2 cools the planet and hence limits ongoing ice melting.
But there lies the rub. We are in an ice-melting phase of the Milankovitch cycle now, where the Earth’s orbit is closer to circular and the Earth’s tilt is closer to perpendicular. But CO2 levels aren’t declining – partly because we’ve chopped a lot of trees and forests down, but mostly because of anthropogenic CO2 production. Without the limiting factor of declining CO2 we’ve seen in previous Milankovitch cycles, presumably the ice is just going to keep on melting as the albedo of the Earth surface declines.
So you might want to rethink that next coastal real estate purchase – or hope for the best from Copenhagen.