GLOBAL WARMING - WHY NOW?

What is Global Warming?

Global warming consists in the observed increase in the average temperature of the Earth’s near surface and oceans in recent decades and its future perspectives of continuation.

During the last century the global average air temperature near Earth’s surface rose 0.74 ± 0.18º Celsius (1.3 ± 0.32º Fahrenheit). The most widespread and mainstream scientific opinion on climate is that “most of the observed increase in globally averaged temperatures since mid-20th century is very likely due to the observed increase in greenhouse gas concentration”, which causes the warming of surface and lower atmosphere by increasing the greenhouse effect.

There are other phenomena which have had smaller but significant effects on global average temperature since 1950 such as solar variation and volcanoes.

As said before, this is the opinion prevailing for the scientific community, but there are a few scientists who disagree about the primary causes. These are the points where they disagree:

• "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities", in particular emissions of the greenhouse gases carbon dioxide and methane.


• If greenhouse gas emissions continue the warming will also continue, with temperatures increasing by 1.4 °C to 5.8 °C between 1990 and 2100. Accompanying this temperature increase will be a sea level rise of 9 cm to 88 cm, and increases in some types of extreme weather. On balance the impacts of global warming will be significantly negative, especially for larger values of warming.

By offering the following arguments they sustain that:

The global warming is unknown: They conclude that it is too early to attribute any cause to the observed rising temperatures, man-made or natural:

• Chris de Freitas, Associate Professor, School of Geography, Geology and Environmental Science, University of Auckland: "There is evidence of global warming. ... But warming does not confirm that carbon dioxide is causing it. Climate is always warming or cooling. There are natural variability theories of warming. To support the argument that carbon dioxide is causing it, the evidence would have to distinguish between human-caused and natural warming. This has not been done." (The New Zealand Herald, May 9, 2006).


• David Deming, geology professor at the University of Oklahoma: "The amount of climatic warming that has taken place in the past 150 years is poorly constrained, and its cause--human or natural--is unknown. There is no sound scientific basis for predicting future climate change with any degree of certainty. If the climate does warm, it is likely to be beneficial to humanity rather than harmful. In my opinion, it would be foolish to establish national energy policy on the basis of misinformation and irrational hysteria." (Testimony before the U.S. Senate Committee on Environment and Public Works, December 6, 2006).


• Richard Lindzen, MIT meteorology professor and member of the National Academy of Sciences: "We are quite confident (1) that global mean temperature is about 0.5 °C higher than it was a century ago; (2) that atmospheric levels of CO2 have risen over the past two centuries; and (3) that CO2 is a greenhouse gas whose increase is likely to warm the earth (one of many, the most important being water vapor and clouds). But - and I cannot stress this enough - we are not in a position to confidently attribute past climate change to CO2 or to forecast what the climate will be in the future.""There has been no question whatsoever that CO2 is an infrared absorber (i.e., a greenhouse gas — albeit a minor one), and its increase should theoretically contribute to warming. Indeed, if all else were kept equal, the increase in CO2 should have led to somewhat more warming than has been observed." (San Francisco Examiner, July 12, 2006 and in Wall Street Journal, June 26, 2006, Page A14).

Global warming is mostly due to natural processes: These scientists conclude that natural causes are likely to be more to blame than human activities for the observed rising temperatures:

• Khabibullo Ismailovich Abdusamatov, at Pulkovskaya Observatory of the Russian Academy of Sciences and the supervisor of the Astrometria project of the Russian section of the International Space Station: "Global warming results not from the emission of greenhouse gases into the atmosphere, but from an unusually high level of solar radiation and a lengthy - almost throughout the last century - growth in its intensity." (Russian News & Information Agency, Jan. 15, 2007).


• Robert M. Carter, researcher at the Marine Geophysical Laboratory at James Cook University in Australia: "The essence of the issue is this. Climate changes naturally all the time, partly in predictable cycles, and partly in unpredictable shorter rhythms and rapid episodic shifts, some of the causes of which remain unknown." (Telegraph, April 9, 2006).


• Philip Stott, professor emeritus of biogeography at the University of London: "...the myth is starting to implode. ... Serious new research at The Max Planck Institute has indicated that the sun is a far more significant factor..." (Global Warming as Myth).

Climate forecasting isn't as accurate as the IPCC ranges imply: Scientists, by saying this, conclude that it isn't possible to predict global climate accurately enough to justify the narrowness of the ranges projected for temperature and sea-level rise over the next century. These scientists don't specifically conclude that the numbers are too high, or specifically conclude that the numbers are too low, merely that the numbers are likely to be inaccurate in either direction due to the difficulty of global climate modeling:

• Hendrik Tennekes, retired Director of Research, Royal Netherlands Meteorological Institute: "The blind adherence to the harebrained idea that climate models can generate 'realistic' simulations of climate is the principal reason why I remain a climate skeptic. From my background in turbulence I look forward with grim anticipation to the day that climate models will run with a horizontal resolution of less than a kilometer. The horrible predictability problems of turbulent flows then will descend on climate science with a vengeance."


• Dr. Ben Herman, University of Arizona Department of Atmospheric Sciences: "When you compare satellite, mid-troposphere satellite observations, with surface observations they don't agree with climate models", "there are all kinds of complicated feedback mechanisms that come into play that the models cannot property handle, " the temperature predictions being made today are done "off the hat and without any backing."

The Intergovernmental Panel on Climate Change (IPCC) reference models predict
that global temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. Such a wide range of values offer many different scenarios of future greenhouse gas emissions as well as uncertainties regarding climate sensitivity. Even if no further greenhouse gases are released after 2100 (most studies focus only on the period up to this date), warming and sea level rise are expected to continue for more than a millennium, due to the long average lifetime of carbon dioxide (CO2) in the atmosphere.

Certain changes can be produce by an increase in global temperatures, such as rising sea level and changes in the amount and pattern of rain fall. Frequency and intensity of extreme weather events may increase thought it is difficult to connect specific events to global warming. Other consequences include changes in agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the exact degree of climate change expected in the future, and especially how changes will vary from region to region across the globe. A stormily contested political and public debate also has yet to be resolved, regarding whether anything should be done, and what could be cost-effectively done to reduce or reverse future warming, or to deal with the expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combating greenhouse gas emissions.