| In February 2007, the Intergovernmental Panel on | | | | effect. It probably has the largest impact on the |
| Climate Change (IPCC) stated in their Fourth | | | | planet's temperature and climatic conditions, much |
| Assessment Report that human actions are "very | | | | larger than CO2. Water particles in the form of clouds |
| likely" (i.e. with 90% or greater probability) the cause | | | | act to reflect incoming solar heat, but the film argues |
| of global warming, indicated by an increase of 0.75 | | | | that the effects of clouds cannot be accurately |
| degrees in average global temperatures over the last | | | | simulated by scientists attempting to predict future |
| 100 years. This statement is the result of very tough | | | | weather patterns and their effects on global |
| discussions on a worldwide scale between thousands | | | | warming. This argument probably is correct and it is |
| of climate researchers whether human activity is the | | | | well recognized that water vapor is responsible for |
| main cause of global warming. The results of this | | | | the natural warming up of the surface temperature |
| discussion were presented to the public in many | | | | to approximately 30-35ºC. Anthropogenic |
| publications, for instance in Martin Durkin´s | | | | greenhouse effect, according to the film’s |
| documentary “The Great Global Warming | | | | argumentation, is only about 2% of the total |
| Swindle”, presented in March 2007 at UK´s | | | | “natural” greenhouse effect, which |
| Channel 4. The main message of this production was | | | | corresponds to a 0.6-0.7 ºC increase in temperature. |
| that man-made global warming is "a lie" and "the | | | | This estimate is somewhat smaller compared to the |
| biggest scam of modern times." Martin Durkin and | | | | results of much more sophisticated simulations (0.9 |
| coworkers argue that the scientific consensus on | | | | – 2.7ºC), but there is undoubtedly an |
| climate change is the product of "a multibillion-dollar | | | | anthropogenic effect of CO2 increasing the average |
| worldwide industry, created by fanatically | | | | surface temperature. |
| anti-industrial environmentalists, supported by | | | | One example of the complexity of climatic simulations |
| scientists peddling scare stories to chase funding and | | | | is the prediction of future storm events considering |
| propped up by complicit politicians and the media". | | | | global warming effects. According to a recently |
| The documentary showcases scientists, politicians, | | | | published study, published online by research |
| economists, writers, and others who are sceptical of | | | | meteorologist Tom Knutson in the journal Nature |
| the scientific consensus on anthropogenic (or | | | | Geoscience and resumed in the New York Times |
| man-made) global warming. Some of the scientists, | | | | (May 18, 2008), global warming isn't to blame for the |
| opposing the main stream of greenhouse gas | | | | recent jump in hurricanes in the Atlantic. The study |
| theories, simply argue that it has not yet been | | | | predicts that by the end of the century the number |
| ascertained whether humans are the primary cause | | | | of hurricanes in the Atlantic will fall by 18 percent. In |
| of global warming or if there are other natural | | | | the past, Knutson has raised concerns about the |
| variations responsible for this phenomenon like | | | | effects of climate change on storms. His new paper |
| increased solar activity, cosmic rays or variations in | | | | has the potential to heat up a simmering debate |
| natural climatic cycles. There is also a series of | | | | among meteorologists about current and future |
| scientists questioning the temperature records used | | | | effects of global warming in the Atlantic. And |
| in the databases as temperature differences | | | | Knutson is not alone with this view. Another group of |
| attributed to the greenhouse effect are reasonable | | | | experts, those who study hurricanes and who are |
| small (fractions of a ºC). The so-called “urban | | | | more often skeptical about global warming, also say |
| heat island” effect leads to a local warming in | | | | there is no link between global warming and hurricane |
| more populated areas, showing slightly higher | | | | frequency. They attribute the recent increase to a |
| temperatures due to to increased heat generated by | | | | natural multi-decade cycle. According to the |
| cities, rather than a global temperature rise. Anyhow, | | | | prediction, the number of hurricanes touching land in |
| this argument was confuted by the IPPC, indicating | | | | the US and its neighbors will drop by about 30 |
| that the effect of the urban heat island on the global | | | | percent because of wind factors. However, the |
| temperature trend is no more than 0.05 °C (0.09 | | | | biggest storms, those with winds of more than 110 |
| °F) degrees through 1990. | | | | mph, would only decrease in frequency by 8 percent. |
| Other facts presented by the film were shown to be | | | | The biggest decrease is forecasted for storms with |
| incorrect or misinterpreted. The film asserts for | | | | winds between 39 and 73 mph (normal tropical |
| instance that records of atmospheric CO2 levels since | | | | storms), who would decrease by 27 percent. |
| 1940 show a continuing increase, but during this | | | | It's not all good news from Knutson's study, |
| period, global temperature decreased until 1975, and | | | | however. His computer model also forecasts that |
| has increased since then. Anyhow, it is well | | | | “hurricanes and tropical storms will be wetter and |
| recognized that this cooling was driven mostly by | | | | fiercer. Rainfall within 30 miles of a hurricane should |
| aerosols (i.e. pollution) in the atmosphere. There is | | | | jump by 37 percent and wind strength should |
| nothing contradictory about this cooling when all | | | | increase by about 2 percent”, Knutson's study |
| sources of radiation changes are considered. A | | | | says. |
| second argument that easily can be invalidated is the | | | | There are already critical reactions on this new |
| impact of the so-called “solar variation | | | | publication. MIT hurricane meteorologist Kerry |
| theory” on global warming. According to the | | | | Emanuel claims that the computer model used by |
| authors, solar activity (and involving cosmic rays as | | | | Knutson is not adequate enough to look at storms |
| well as heat from the sun aiding cloud formation) is | | | | and according to Kevin Trenberth, a climate scientist |
| currently at an extremely high level and directly linked | | | | from the National Center for Atmospheric Research |
| to changes in global temperature. The film argues | | | | in Boulder, Colo., Knutson's computer model is poor at |
| that solar activity is far more influential on global | | | | assessing tropical weather and ''fail to replicate |
| warming than any other anthropogenic or natural | | | | storms with any kind of fidelity.'' It also does not |
| activity on Earth. What the film does not mention is | | | | considering well enough the intensity, duration and |
| that solar activity has declined over the last 30 years | | | | size of the storm events, as not only the number of |
| - at the same time as the major spike in global | | | | hurricanes is important to evaluate. |
| temperature. | | | | Positive feedback comes from NOAA hurricane |
| But there are some statements related to the | | | | meteorologist Chris Landsea , who wasn't part of this |
| influence of the oceanic mass and water vapour on | | | | study, praised Knutson's work as ''very consistent |
| climate change which are more difficult to confute. | | | | with what's being said all along.'' ''I think global |
| Water vapour makes up about 98% of the | | | | warming is a big concern, but when it comes to |
| greenhouse gases by volume and provides something | | | | hurricanes the evidence for changes is pretty darn |
| between 40 to 80 percent of the natural greenhouse | | | | tiny,'' Landsea said. |