Pacific Northwest Climate Variability

Wrap-up from Global Warming Debate

• "Fessing Up"
  • Stepped over the line by using specific extreme events (storms) and attributing them to global warming (remember in class that seperating the climate influence on specific storms is very difficult).
  • The "con" case had some very good arguments; especially related to:
    • The surface temperature trend is not continuously upward during the 20th century.
    • The warming rates are not explained by any simple model incorporating an increase in greenhouse gas concentrations (i.e., the 20's experienced warming similar to the 90's).
    • There are some real issues remaining in the difference between surface and satellite observations of temperature. Current research has highlighted that these different modes of observation are both believable (i.e., there is enough data and checks to believe that the lower atmosphere is warming less than the surface, but there is also enough data to believe the surface temperature trend).
  • Beware of the scientist that gives only glib answers in repsonse to these areas of scientific uncertainty.

• "Fessing Up"
  • Guilty of over-emphasizing global means: 2 degrees Celsius over the whole globe (averaged over land/water) *IS* a pretty big deal (much more warming expected over land, especially at high latitudes). Global means do not provide any of the regional information important to decision-making, nor do they acknowledge the fact that local impacts can be felt due to very small changes in the mean (e.g., changing the distribution of water in the west).
  • Saying that there will be "economic balance" between winners and losers is highly uncertain (though it was sort of assumed in the "con" argument). It is likely true, however, that the "pro" side of this argument is also not true (that all changes will be damaging and all damages will be extreme).
  • Catastrophic scenarios are not amenable to "risk analysis". Personal values must enter into the equation which are not within the academic area of calculating damages.
  • Twisting information to make a point (advocacy rather than science). The biggest example the "con" case used was the temperature trends in urban/rural California to show that the surface is only warming in urban areas. This is a very specific location (CA) where almost all the large population centers are on the coast. The ocean provides a "temperature buffer" and has kept the warming down in this specific region. However, the "pro" case highlighted that the general warming, over the whole globe, is more broad than this and includes warming at rural sites as well as urban ones.

• Both sides were guilty of using a 20-year trend to try and make much broader arguments about the warming (or non-warming) signal. 20 years is too short a period to tell us about the greenhouse gas-induced changes (because of the patterns of natural variability and solar variability). In other words, both sides were guilty of distorting/misrepresenting data to support a particular political agenda.
• Though science is not meant to be a democratic process (i.e., you can be right but unpopular), it is important in the climate change area to recognize that the vast majority of atmospheric scientists do believe that climate change must result due to increasing concentrations of greenhouse gases. The handful of credible dissenters sometimes have excellent questions, but generally do not provide an alternative hypothesis for how the earth/atmosphere system will readjust due to an enhanced greenhouse effect.
• Sound bites from scientists are interesting, but really not that useful in terms of informing a decision-maker or the public.
• Related to this, getting people from extreme opposite ends of the spectrum to talk about science controversies is interesting (and often comical), but really not that useful to inform the public or to inform decision-making. The arguments presented in this kind of forum are often esoteric and are more appropriate for Jerry Springer than a discussion about policy/management choices.
• Finally, both sides tried to apply socio-economic "damages" or "benefits" to their particular view of the world. There are a few important lessons here. First, economics is a study which concerns a wide range of options available to a perfectly informed decision-maker. As such, applying economics to scenarios of future climate is risky because almost any scenario can be created depending upon how you attribute climate "damages" or "benefits". In other words, the same climate scenario could be interpreted to be very good for society or very bad, depending on the assumptions of your analysis. Second, the core of economic theory is based on marginal changes to the way things are done. This is appropriate for looking at gradual changes in climate and the associated decision-making process, but inappropriate for dramatic changes or responses to extreme events. Third, always be cautious of those "experts" who are all too willing to talk about another discipline without formal training in that area.

It's likely wise to trust in some of the science you've heard or read this quarter:

• The Earth has warmed over the 20th century (though this has not been uniform in time and the satellite warming doesn't match the surface warming well). This has amounted to about a degree F averaged over the whole globe as compared with pre-industrial times.
• There is a natural greenhouse effect which has been understood for a very long time.
• Greenhouse gas concentrations in the atmosphere are increasing and carbon dioxide is roughly 1/3 higher than it was in pre-industrial times. There is a link to human activities in these concentrations from fossil fuel use, deforestation and other human-controlled processes (for example, some greenhouse gases did not exist before the industrial age and others are present at much higher concentrations).
• Aerosols (specifically sulfate aerosols) which have a cooling effect, have also been increasing since the beginning of the industrial age.
• Almost all plausible scenarios of the future indicate that greenhouse gas concentrations will continue to increase. This is almost certain to be true due to inertia in both socio-economic systems as well as in the earth/atmosphere/biosphere system.
• Significant uncertainties remain in our understanding of 20th century warming and cooling and the discrepancy between satellite and surface temperature observations.