Monday, January 28, 2013

Global Warming Update: New Data

In October 2012 the Meteorological Office’s Hadley Center in England, one of a handful of research centers that maintain global temperature databases, released the HADCRUT4 data set, which shows no net global temperature change since 1997.  This is in stark contrast to the clear temperature rise from 1968 to 1998, a change of +0.7 oC in 20 years, for a warming rate of 0.035 oC per year.  The HADCRUT4 data can be seen at
The Met Office followed up this disclosure with a projection of future warming trends (issued, strangely enough, during the Christmas holidays, and consequently largely missed by the press).  In it they predict what they call a “continuation of global warming” over the next five years, reaching a “temperature anomaly” of 0.55 oC by the year 2017. This phrase means that the temperature increase in 2017 relative to the average base reference temperature for the years 1961-1990 will be 0.55 oC.   Somehow they neglected to mention that the actual observed temperature anomaly has hovered around the +0.5 oC level since 1998: in other words, it will not be significantly warmer in 2017 than it is now.  From 1997 to 2017, according to the Hadley Center’s best estimates, we will have had 20 years without any global warming.

Last week Jim Hansen, a prominent climate modeler at NASA’s Goddard Institute of Space Studies (GISS) in New York City, concurred with the Hadley Center’s historical data.  Dr. Hansen was one of the earliest and most vocal proponents of the idea that human activities, especially burning of fossil fuels, are responsible for global warming.  GISS also finds that the “five-year running average” of global temperatures, spanning 14 years of data, has not changed in the past decade.  This standstill in warming, which was not predicted by any of the climate models, reminds us of the primacy of data over both enormously complex (but still oversimplified) computer models and faith-based beliefs.  It also presents a fresh challenge to climate modelers.

Then, two days ago, Dr. Terje Berntsen, a professor at the University of Oslo’s Department of Geosciences and a senior research fellow at the Center for International Climate and Environmental Research in Oslo, released a reassessment of the warming effects of carbon dioxide.  His research, incorporating the data showing the last decade and a half of no net global warming, revealed that the “climate sensitivity” for carbon dioxide is about 1.9 oC per doubling of CO2, far below the numbers often quoted in the media. 

 “Earth’s mean temperature rose sharply during the 1990s. This may have caused us to overestimate climate sensitivity,” Prof. Berntsen explains.  “We were most likely witnessing natural fluctuations in the climate system – changes that can occur over several decades – and which are coming on top of a long-term warming.”  Also recall that Prof. Ramanathan’s data suggest that soot has two thirds as large a warming effect as CO2 does, so that 40% of the total warming should actually be attributed to soot.  Then the climate sensitivity is only about 1.2 oC per doubling of CO2.  Of course, the present temperature plateau was not predicted by our models. Predicting the future effects of soot is hard because controlling soot production is relatively easy compared to controlling carbon dioxide release.  Future soot emissions from diesel engines and coal-fired power plants will reflect legal and regulatory rules that do not yet exist, and which therefore defy prediction.

We are reminded of the immortal words of that great philosopher, Yogi Berra: “The trouble with predicting the future is that it is very hard.”


Wednesday, January 16, 2013

Curiosity about Life on Mars

The Curiosity rover is preparing to drill a little hole in a slab of Martian sedimentary rock to extract material for testing in the ongoing search for life on the red planet.  What can we expect to find?  What was the environment like for the origin and evolution of life forms on Mars?

               We know far more about the present physical and chemical conditions on the surface of Mars than we know about the distant, presumably warmer and wetter, past.  Since Mars has a thin, very dry atmosphere of 97% pure carbon dioxide, ultraviolet (UV) light from the Sun readily penetrates to the surface.  In the absence of more than a tiny trace of oxygen, ozone cannot be made in quantity, and cannot provide an ozone layer similar to Earth’s to protect the surface from killing UV radiation.  In fact, UV light can dissociate carbon dioxide into carbon monoxide (CO) and atomic oxygen (O) even at the surface of the planet.  Even a tiny trace of atomic oxygen is very bad news for organic matter: O is a very powerful oxidizing agent.  Any organic matter exposed at the surface of Mars, whether exposed by weathering of ancient organic-bearing sediments or dropped onto Mars by impacts of carbonaceous meteorites, would quickly ”burn” into carbon dioxide and water vapor.  It is only in the interiors of ancient sedimentary rocks, where O cannot penetrate, that organic matter might survive. 

               The CO2 content of the atmosphere of Mars is sufficient to provide an average pressure of about 0.006 atmospheres at the surface, although this number is very variable from place to place because of the wide range of elevations spanning a deep basin (Hellas) and several towering volcanoes.  The CO2 famous for maintaining Earth’s surface temperature above the freezing point (via the greenhouse effect) has a surface pressure of less than 0.0004 atmospheres.  So why is Mars so cold?  Several reasons: the greenhouse effect on Earth is dominated by water vapor, which is very rare on Mars; Mars experiences about half the intensity of sunlight that Earth receives.  So an earlier, warmer Mars requires that it was also a wetter Mars.  You need water vapor to make Mars warm enough to have water vapor!   Given favorable early conditions on Mars, with liquid water present and a strong greenhouse effect at work, life may indeed have originated there.  But what evidence of that former life would we be able to find today?  There are two obvious possibilities: well-protected organic matter deep inside ancient sedimentary rocks, or fossils of simple life forms.  But evidence of ancient life would not necessarily prove an independent origin for life off Earth: large impact events can launch surface rocks from both Earth and Mars into orbits around the Sun, from which they can collide with and land on either planet.  Martian life, if any, may be expatriate Earth life--- and vice versa.

Carbon and Climate: A Victory of Data over Models

The story of the impact of carbon dioxide (CO2) on climate is widely reported, but the media reports often confuse matters needlessly by referring to CO2 as “carbon”.  In the real world, combustion of both biomass and fossil fuels injects carbon dioxide, water vapor, and incompletely burned carbon (soot, carbon black, or “black carbon”) into the atmosphere.  All three influence the warming and cooling of Earth.  Although the strongest greenhouse effect of these three is due to water vapor, generally the amount added by combustion is dwarfed by the natural background due to the humidity of the atmosphere (although matters would be different if we flew fleets of supersonic aircraft in the naturally dry stratosphere).  Carbon (soot) has long been suspected as a contributor to heat capture by the atmosphere.  Dr. V. Ramanathan at Scripps Institution of Oceanography suggested back in 2008 that, based on observational data, carbon black was almost as important as CO2 in governing heat capture by the atmosphere. Climate modelers generally dismissed his arguments, but the data continue to accumulate-- and now we find in the latest issue of the Journal of Geophysical Research that Dr. Ramanathan was right after all.  In its coverage of this emerging story, the Washington Post comments that “many researchers questioned his analysis because it was based on observations rather than computer modeling”.  And so it was.  How shocking!

The process by which we favor observational evidence over theoretical models has a name: it is called “science”.  We scientists revise our models to conform to observation; it is grossly dishonest to reject observational evidence simply because it fails to conform to current theories.  Let us hope that the results of these observations will soon be evident in improved computer modeling in which the warming effects of carbon are better accounted for and the supposed impact of CO2 on warming is proportionately reduced.  Perhaps the anomalous leveling out of observed global temperatures (observed as opposed to predicted by models) over the last 16 years can be better understood when the effects of soot are properly accounted for.  How important is soot?  The latest estimate is that it is two thirds as important as CO2.  So please, science writers, stop calling CO2 “carbon” and start considering real carbon.  It’s a very big deal.