Let me add my two cents here. As a scientist that has worked on several models such as these and worked in field research facilitys, national labs, and universities on climatology, oceanographic, and numerous physics modeling and field work (DoE type of work) - I've got a pretty good idea of what we have learned.
Problem is always with scale - how far do you look back, how long will these processes take, how soon is too soon, how late is too late, etc. Also depends on where and how the information is being presented - is it from a climatologists (hundreds to thousands of years scale) or meterologists (hours, days, years scale).
As for pulling trends from past years datas, or even looking at data from the past 3 years, or 5 years, or even 10-20 years ago - may look very impressive - but you cannot accurately paint a picture if you look at only aspect on a microscoptic scale. Many make for more exciting reading or spawn a good number of publications, but does little to advance the scientific community's understanding.
Here are some of the most common misconceptions to date (As told by George Taylor, Climatologist at Oregon State University's College of Oceanic and Atmospheric Sciences, President - American Association of State Climatologists, Memeber - American Meteorological Society)
HYPE
Global warming may lead to an ice age.
TRUTH
The idea of “global warming creating an ice age” is based on a historical event that DID happen. And can’t history repeat itself? The Younger Dryas period was a sudden “mini ice age” that occurred 10,000 or so years ago when global warming (caused by the end of the last ice age) melted large amounts of continental ice, releasing massive amounts of fresh water and changing the course of ocean currents. But the ice over North America at the time was a mile thick! Sea levels were 200 feet lower than at present. One cannot compare the Younger Dryas with the 21st century!
HYPE
Weather extremes such as droughts, floods, hurricane, tornadoes, and heat waves have become more common.
TRUTH
Scientists have studied this issue and come to the opposite conclusion: extreme events are becoming LESS common. Atlantic hurricanes were much more numerous from 1950 to 1975 than from 1975 to present. Hailstorms in the US are 35% less common than they were fifty years ago. Extreme rainfall in the US at the end of the20th century is comparable to what it was at the beginning of the 20th century. Roger Pielke, Jr, in the journal Climatic Change (1999) said “it is essentially impossible to attribute any particular weather event to global warming." For flooding, Pielke did list a number of important non-climatic factors that have the potential to influence flooding in the future, including deteriorating dams and levees, changes in land use, building in flood-prone areas, governmental policies, as well as other societal influences. Pielke, R.A., JR. 1999. Nine fallacies of floods. Climatic Change 42: 413-438.
HYPE
In the United States, recent years have been the warmest on record.
TRUTH
The warmest decade in the last 100 years in the U.S. was the
1930s; the warmest year was 1934.
HYPE
Climate has been stable for a long time but now is getting increasingly extreme.
TRUTH
Climate is always changing, on a variety of time scales – from a few years to millennia. There is strong evidence that climate variability is greater during cold periods than during warm periods, so a moderate warming would appear to produce a more stable climate.
HYPE
CO2 is a pollutant.
TRUTH
CO2 is an essential nutrient for plants. Plants absorb CO2 and release oxygen, while animals inhale oxygen and exhale CO2. Researchers have proven that higher CO2 concentrations enable plants to grow faster and give them better drought tolerance.
HYPE
CO2 is the most important greenhouse gas.
TRUTH
Not even close. Most of the greenhouse effect is due to water vapor, which is about 100 times as abundant in the atmosphere as CO2 and thus has a much larger effect.
HYPE
The greenhouse effect is a bad thing.
TRUTH
The greenhouse effect is necessary for life on earth as we know it, were it not for the greenhouse effect, temperatures on Earth would be about 60 degrees F (33°C) colder than they are at present. The global warming discussions center on the claims that human enhancement of the greenhouse will raise temperatures, and that these will be large compared with natural variations.
HYPE
Modeling the earth's climate is nearly an exact science.
TRUTH
General Circulation Models (GCMs) vary by a factor of 3 in their forecasts; they require arbitrary adjustments; and they cannot properly simulate clouds. Their forecasts of substantial warming depend on a positive feedback from atmospheric water vapor (WV). Many of the natural variations (sunlight, El Niño, volcanoes, and so on) cannot be predicted with any skill in the future.
HYPE
The sun is a constant source of energy.
TRUTH
The sun’s radiation varies over many time scales, from short (11 year sunspot cycle, 20-27 year magnetic field) to medium (170- and 210-year cycles) to long (tens of thousands of years). Northern hemisphere temperature variations over the last 200 years closely match estimated solar intensity, as one would expect.
HYPE
Glaciers all over the world are letting because of global warming.
TRUTH
Actually, this is somewhat true, but it is unlikely that changes in glaciers are affected by recent climate changes. According to the Glacier Program at Rice University (http://www.glacier.rice.edu), the response time to climate changes for different sizes of glaciers are as follows:
ice sheet 100,000 to 10,000 years
large valley glacier 10,000 to 1,000 years
small valley glacier 1,000 to 100 years
For very large glaciers such as the Antarctic Ice Sheet, considerable time is needed for the ice sheet to respond to any environmental changes. Changes in climate may take tens of thousands of years before the entire ice sheet has adjusted to changing, and by that time, the climate may have changed again.
HYPE
Summers will be extremely hot and dry.
TRUTH
According to greenhouse physics, the effects of increases in greenhouse gases will be much more significant in the driest air. This occurs in the coldest regions (cold air is able to hold much less water, in the form of water vapor, than warm air) – the polar regions, in winter, at night. Temperature effects in tropical or mid-latitude regions and in summer are expected to be much less significant.