Category Archives: what is global warming?

Global Warming Maps/Graphs

Two years ago I made a post that featured a dozen or so maps and graphs that lended insight into global warming. It turned out to be one of the most read pages on my site. I now want to update that page with even better and a larger number images which are relevant to climate change. They will feature only very brief explanations. Most of what is being shown is self-evident, but if you have questions, feel free to ask them. Hopefully this can serve as a good reference for those who want some images relevant to global warming. I also recommend the site http://www.globalwarmingart.com. These images can all be clicked on for enhanced view. I am also happy to take further suggestions and them.

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Richard Alley at AGU 2009: The Biggest Control Knob

The webcast for Dr. Alley’s presentation is now up, so I recommend watching the video. It is concerning the role of CO2 on climate over geologic time.

As my own side note, Alley is one of my favorite scientists…he’s pretty much “the guy” when it comes to ice core work and has done a lot with paleoclimate (over the ice core record especially), abrupt climate change, glaciology, and sea level rise. He’s a very interesting character who always puts things in a nice perspective, and often humorous ways of teaching (e.g., his Johnny Cash geology lesson).

Re-visiting climate forcing/feedback concepts…

I haven’t been able to post much lately, so I just want to put in this post which outlines some of the basic radiative forcing and feedback physics which climatologists use to assess climate change. This is fairly standard material which should be understood by anyone with a deep interest in climate. This article is a bit lengthy so hopefully you have the patience to go through it (or put it on your favorites and come back). Also, a lot of discussion has come up recently over Richard Lindzen’s ERBE analysis in which he purports to show that global climate sensitivity is small, and that the net effect of climate feedbacks is to dampen the so-called Planck response. That basically provoked this post. I’m going to define all these terms below, so don’t worry if I’ve already lost you, and while I am going to do some math in this post, it should be accessible to most people who know a bit of algebra. Skipping over a few calculus steps won’t be detrimental and I’ve tried not to assume much climate background (although I do link to some side references for clarification on some matters). My focus is not on Lindzen’s analysis here, which I don’t feel to be robust at all, but rather building up simple mathematical models for understanding climate change. This will not be new to anyone who has followed the climate literature or discussions for some time, but hopefully it can be helpful to some, or at the very least, serve as a useful reference.

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Cycles, projections, and other lingo

So I was at work today, and with all the bad weather he had plenty of time to shout at the boss and another co-worker about global warming.  It was a good 2-on-1 handicap match. “Talking” debates are not really my thing since no opportunities exist to check claims, reference sources, show graphs, etc that you could do in online/text correspondence, and so basically anything goes.  Even totally wrong claims like “Volcanoes spit out more pollution than humans do.”

 The boss and the co-worker were very skeptical.  I’m not sure how scientific our exchange was– they spent most of the time trying to convince me I should be very cautious in trusting the general scientific community, and I spent most of the time telling them that they should trust physics, but no one budged.  They’re intelligent group of folk (one trained in biology) but not really familiar with the climate science literature, so I tried to avoid ideas like “radiative forcings,” “water vapor feedback,” “stratospheric cooling,” and other concepts.  So we didn’t really discuss “how CO2 influences climate” or even radiative feedbacks, and it probably was worthwhile as a philosophy of science talk if anything.

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Feedbacks, Sensitivity, and Practical application

The global, annual-mean surface temperature is the most widely used measure of climate change. In particular, scientists are very interested in how the globally averaged temperature will respond as a function of changed amounts of greenhouse gases in the atmosphere, changed amount of solar intensity, etc. The term “climate sensitivity” refers to how much temperature change the planet experiences from a given “forcing.” A forcing is an imposed change of the planet’s energy balance with space.

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Palin on Climate Change

Andy Revkin has a good writeup on the interview between Sarah Palin and Katie Couric. In the interview, Sarah Palin makes many fuzzy points which Andy Revkin (as I) request clarification: what does ‘pollution’ mean? How do we solve a problem if we don’t care what the causes are?

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On the Arctic sea ice

Sea ice extent in the Northern Hemisphere has exhibited large and anomalous declining trends over the last several decades. In particular, there has been over a 20% decline since 1979. Linear trends in arctic sea-ice extent since 1979 are negative in every month.Recently, there has been particular interest recently over a record-breaking year in 2007 which flew by the second-lowest year in 2005. There also has been a foot-race this year, which has kept me particularly interested over the last few weeks. For a while, it seemed that 2008 would clearly not surpass 2007, but due to the drop over the last few weeks, that may not be the case (although it probably will be). Sea ice extent as of September 7, 2008 is 4,739,844 km2, while 2007 minima reached 4,267,656 km2 on September 16th last year.

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Tipping Points in the Earth’s Climate System

Modern climate science tells us that increased emissions of greenhouse gases, most notably carbon dioxide, will change the climate that we are used to and have consequences for ecosystems and societies worldwide. A rise of just several degrees can have large and widespread impacts that dramatically alter civilization, but there are worries aside from a slow and steady rise. Climatic records show that large, widespread, and abrupt climate changes have occurred repeatedly in the past. Dr. Richard Alley of Penn State University has lectured on this topic and has used an analogy of the climate being like a drunken college student– when you don’t do much to it then it will just sit there, but if you move it around a little bit then it will stagger about and maybe fall. The last ten thousand years or so (the Holocene) has been an unusual time of relative calmness, with little variation in the climate. However, for most of the last 100,000 years, and even before, this has not been the case. One of the potential threats that comes from altering the chemistry of the atmosphere, and changing the land around to suit or needs, is the ability to flip a “climate switch” and force it between different states. Other possibilities include crossing critical thresholds, such as melting the arctic sea ice, that will have large socio-economic and/or ecological consequences. Such events have been labeled “tipping points” and many scientists (notably James Hansen of NASA, Alley, and others) have started to issue many warmings that the Earth may not respond to a new climate is a nice and steady fashion.

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Physics of the Greenhouse Effect Pt 2

In the preceding post, on the greenhouse effect, I investigated the role of the greenhouse effect and its play in radiative balance, and how the presence of an atmosphere acts to raise planetary temperatures. The take home points should be that for a planet with no infrared absorbing layer above the surface, the fourth power of the surface temperature always approximates a value determined by the incoming solar radiation. The only way the surface temperatures can exceed this value is if there is an atmosphere which acts to be a blanket to outgoing radiation. A planet can also be heated by internal processes such as radioactive decay or rigorous convections from the mantle, but these are rather negligible on the terrestrial planets. Adding greenhouse gases to an atmosphere whose temperature decreases with height must act to warm the surface by making the net downward emission greater than zero. In this post, I will elaborate on specific greenhouse gases, the runaway greenhouse effect, and an antigreenhouse effect.

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Physics of the Greenhouse Effect Pt 1

Jean Baptise-Fourier is generally credited with the discovery of a greenhouse effect, which involves the process by which the presence of an atmosphere acts to raise the surface temperature of a planet. This was extremely simplified at the time, and the term greenhouse never appears in his 1827 writing, but he did establish the effect that the atmosphere had on incoming light and outgoing infrared (heat) radiation, and that some heat was absorbed by the atmosphere which was opaque in the infrared but transparent to incoming solar energy. A copy of his essay, translated by R.T. Pierrehumbert can be found here. We’ve made a lot of progress since then, as Svante Arrhenius began to quantify the phenomenon nearly 75 years later, the work of Stefan and Boltzmann established the relationship between an object’s temperature and its outgoing radiation, the role of convection and water vapor and clouds turn out to be important in more complex models developed later, etc. The pionerring paper by Arrhenius, entitled On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground, which is the famous 1896 piece, began to investigate what the effects of doubling the atmospheric CO2 content would be. At this time, most of the interest in the subject was in solving the mystery of the coming and going of ice ages. Like most pioneering efforts, Fourier or Arrhenius did not have the last word, and we still have much to learn today, but they provided a big leap in how we understand planetary temperatures and the role of the atmosphere in radiative balance. Fourier was one of the first to speculate that human activities could influence climate, and such topics are rather important in modern times.

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