Using the 30 year mean, the hottest 28 years of the record are the past 28 in exact sequential order. In terms of the single years, the hottest 23 have been in the past 28 & the hottest 12 have been the past 12. A period of 30 years was chosen because that is the definition of climate and is the span of the reference period that HadCRU (1961-1990) is based on. The HadCRUT3v temperature record covers 1850 - current.

Using the 30 year mean, the hottest 29 winters (Dec-Jan-Feb) of the record are the past 29 in exact sequential order. In terms of the single winters, the hottest 9 have been in the past 12. 2009 is ranked #9 & is 0.4° above the recordset's 1961-1990 baseline average. A period of 30 years was chosen because that is the definition of climate and is the span of the reference period that HadCRU (1961-1990) is based on. The HadCRUT3v temperature record covers 1850 - current.

The cooling of 2007 & 2008 is expected as it was caused by the Southern Oscillation, i.e. La Nina & El Nino. 1997-8 was the strongest El Nino of record. 2008 was the hottest La Nina-influenced year with no El Nino ever recorded. This is why pointing solely to the temperature difference between 1998 and 2008 is not relevant to a discussion of the long-term trend.

Is the climate warming or cooling?

Numerous websites, blogs and articles in the media have claimed that the climate is no longer warming, and is now cooling. Here we show that periods of no trend or even cooling of the globally averaged surface air temperature are found in the last 34 years of the observed record, and in climate model simulations of the 20th and 21st century forced with increasing greenhouse gases. We show that the climate over the 21st century can and likely will produce periods of a decade or two where the globally averaged surface air temperature shows no trend or even slight cooling in the presence of longer-term warming.

Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used. If tree-ring data are used, the conclusion can be extended to at least the past 1,700 years, but with additional strong caveats. The reconstructed amplitude of change over past centuries is greater than hitherto reported, with somewhat greater Medieval warmth in the Northern Hemisphere, albeit still not reaching recent levels.

Internal thicknesses of the ice sheets are increasing as total ice mass is decreasing. This is exactly as expected as increased heat will cause increased evaporation which will result in increased precipitation. i.e. the center gets thicker which the edges melt away.

Arctic sea ice has declined dramatically over at least the past thirty years, with the most extreme decline seen in the summer melt season.

From February 2003 to January 2008, Greenland lost mass at a rate of 179 Gigatonnes per year. The rate is also increasing over time, suggesting an acceleration of mass loss.

Ice loss in Antarctica increased by 75 percent in the last 10 years due to a speed-up in the flow of its glaciers and is now nearly as great as that observed in Greenland

A comprehensive study of Antarctica’s ice confirms that the polar cap is shrinking. In 2006 alone, Antarctica lost nearly 200 billion tonnes of ice

The hole in the ozone layer above the South Pole causes cooling in the stratosphere. This increased circular winds around the continent preventing warmer air from reaching east Antarctica and the Antarctic plateau. The flip side of this is the Antarctic Peninsula has "experienced some of the fastest warming on Earth, nearly 3°C over the last half-century".

While East Antartica is gaining ice due to increased precipitation, Antartica is overall losing ice. This is mostly due to melting in West Antarctica which recently featured the largest melting observed by satellites in the last 30 years. As well as melting, Antartic glaciers are accelerating further adding to sea level rise.

Significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1 °C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface temperature trend is positive.

Take a full pan of salt water with ice in it. Heat the water to melt the ice. Does the pan overflow? Yes. Water with a lower salinity has a lower density, thus more volume.

The correlation between sun and climate ended in the 1970s when the modern global warming trend began. The sun has shown a slight cooling trend over the last 3 decades. Not only is the sun not contributing to global warming, it has had a slight, long term cooling effect.
(This site provides numerous references to primary peer-reviewed journal papers & datasets.)

To forestall the usual response: Yes, the Sun is the primary source of heat here on Earth. When the solar intensity is steady, or slightly decreasing, and the temperature is significantly increasing, it can be reasonably stated that there is another forcing agent in the mix.

There was no 1970s "global cooling scare" in the scientific literature. Time and Newsweek, and all popular weeklies & dailies, are not reliable sources of scientific knowledge.

A review of the literature suggests that, to the contrary, greenhouse warming even then dominated scientists’ thinking about the most important forces shaping Earth’s climate on human time scales. More importantly than showing the falsehood of the myth, this review shows the important way scientists of the time built the foundation on which the cohesive enterprise of modern climate science now rests.
The survey identified only seven articles indicating cooling compared to 42 indicating warming.

Yes, Mars is warming. However, Mars's orbit is more eccentric than Earth's and its climate is dominated by planet-wide dust storms. Mars doesn't have oceans, doesn't have rain, has an atmosphere entirely different from Earth's, and has huge dust storms that noticeably impact the climate. Since there is no rain, the dust lingers in the atmosphere. The dust storms produce large year-to-year variability, large regional changes, and can cause albedo changes by exposing or covering up dark underlying rocks.

The first quantitative scientific research on CO2-moderated global climate change was carried out in the late 19th century by Svante Arrhenius. This research has been numerously independently repeated & validated as the spectral absorption of carbon dioxide is readily measurable. It has been known for over 50 years that an increased atmospheric CO2 concentration will make for a stronger greenhouse effect regardless of saturation in the lower atmosphere.
On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground (1896)
The Infrared Absorption Spectrum of Carbon Dioxide (1932)
Effect of Carbon Dioxide Variations on Climate (1956)
On the Influence of Changes in the CO2 Concentration in Air on the Radiation Balance of the Earth's Surface and on the Climate (1963)
The Effects of Doubling the CO2 Concentration on the climate of a General Circulation Model. (1975)

A doubling of the atmospheric CO2 concentration produces a temperature rise of between 1.5 and 5 degrees Celsius. The variability is based on "tipping points" where natural positive feedback cycles take over and accelerate the process. Claiming that such feedback is "not our fault" is exactly like claiming an alleged arsonist didn't burn down a building because he only lit the match. One example of a tipping point would be the melting of the permafrost, which would release vast amounts of methane into the atmosphere.

Since the start of the industrial revolution, humanity has put out 1.2 trillion tons of CO2, half of that since the early 1980s. The atmospheric CO2 concentration has increased ~40% solely due to our emissions. That increase can be directly linked to humanity through parallel decline of the 14C/12C ratio of atmospheric CO2. That is because fossil fuels do not contain 14C precisely because they are fossil - much older than 10 half-lives of 14C.
- table H.1co2 =>

Water vapor is the most powerful greenhouse gas, however it has a very short atmospheric residence time, on the order of 8-9 days. The concentration of water vapour in the atmosphere is a function of ocean and air temperature that is described by the Clausius-Clapeyron relation. Any excess water vapor in the atmosphere is precipitated out, e.g. rain, and any lack is brought into the atmosphere via evaporation. There are no such "quick fix" processes for the atmospheric CO2 concentration.

The natural CO2 sources do outgas significantly more CO2 than mankind emits through the burning of fossil fuels, however that is only one side of the natural cycle. The oceans are a net CO2 sink that are currently absorbing 7 billion tons more than they outgas each year. The oceans have also played a major role as a sink for up to 30% of the anthropogenic CO2 produced during the industrial revolution. The terrestrial biomes are also a net sink that are currently absorbing 5 billion tons of CO2 more than they outgas each year.

Volcanoes emit 100 - 250 million tons CO2 / year globally; that includes both subaerial and submarine volcanoes, about in equal amounts. Measurements of CO2 levels over the past 50 years do not show any significant rises after eruptions. The most actively degassing volcano in the world, Mt. Etna in Italy, emits ~14 million tons CO2/year. Humanity emitted 28 billion tons of CO2 in 2005 from the burning of fossil fuels. That is more than all volcanic emissions during the entire 20th century.
- table H.1co2 =>

The increased atmospheric CO2 is good for the plants. However, the forecasted CO2 boost - as much as 10 percent - in crop growth will be more than offset by the 20 to 40 percent drop due to higher temperatures alone—and will be further exacerbated by any drying.

The historical temperature changes were primarily caused by Milankovitch Cycles, orbital parameters of the Earth, which caused changes in the solar irradiance. There were, of course, singular events such as comet strikes & super-volcano eruptions that caused significant changes. When the solar irradiance increased, the oceans would warm up and release CO2 into the atmosphere; as can be demonstrated by warming up a carbonated beverage. The increased atmospheric CO2 concentration kept more solar energy in the atmosphere, which warmed the oceans further releasing more CO2. The amount of water vapor also increased, further increasing the temperature. As more ice melts from the warmer temperatures, the Earth's albedo (reflectiveness) changes because dark oceans absorb more energy than the white ice did. There are many feedback cycles, so CO2 being a lagging indicator does not disprove its spectral absorption anymore than an automobile engine charging a battery proves the battery can't start the engine. Natural climate change does not disprove anthropogenic climate change anymore than the preponderance of natural death can be used to disprove homicide.

The historical CO2 concentration temperature lag was predicted years before it was discovered.

It is quite clear that warming of the atmosphere produces wetter wet areas and dryer dry areas.

Weather patterns will keep changing toward an intensified water cycle with stronger floods and droughts. Most regions now subject to droughts will probably get drier (because of warmth as well as less precipitation), and most wet regions will get wetter. Extreme weather events will become more frequent and worse.

At decadal time scales, on a global basis, the model reproduces the observed drying trend (decreasing PDSI) since 1952. An optimal detection analysis shows that there is a significant influence of anthropogenic emissions of greenhouse gasses and sulphate aerosols in the production of this drying trend.
the proportion of the land surface in extreme drought is predicted to increase from 1% for the present day to 30% by the end of the twenty-first century.

Together, the global land areas in either very dry or very wet conditions have increased from ~20% to 38% since 1972, with surface warming as the primary cause after the mid-1980s. These results provide observational evidence for the increasing risk of droughts as anthropogenic global warming progresses and produces both increased temperatures and increased drying.

Both terms, "climate change" and "global warming", are accurate. It is called "global warming" because the averaged temperature is rising. It is called "climate change" because the increased energy (i.e. temperature) won't affect all locales equally. "Climate change" isn't a new term; it's the IPCC, not IPGW & the first assessment report was released in 1990. It has been called "climate change" since 1975.

Carbon offsets ("credits") can be a total advertising gimmick and money-shuffling scam, just like any other activity. However, the concept carbon offsets, and any deceit promulgated in its name, is based on is valid. Carbon dioxide is a globally well-mixed gas. Hence, removing CO2 from the atmosphere at any point on the planet balances out adding CO2 to the atmosphere at any other point on the planet. How, and even if, that CO2 removal is accomplished is where the duplicity & deceitfulness comes into play.

CO2 physically removed ("captured") from the atmosphere, e.g. GRT's ACCESS system, is wholly different than campaigns to plant a tree (short term organic storage) or invest in solar/wind/etc... R&D (high potential of flaky accounting). There is also the case of outright fraud, where money is taken & no service is performed.

Carbon offsets are the stopgap for the fact that change takes time and an acknowledgment that you are creating a mess and paying to clean it up.

All breath is "carbon neutral" as the carbon in the exhaled CO2 was recently extracted from the atmosphere by plants. If plants weren't eaten to get the carbon, animals that ate the plants were.

Even if a poll is conducted legitimately, it is irrelevant to the validity of the scientific knowledge in question. Scientific knowledge is not established by a "yes / no" opinion poll. The Oregon Petition, recently renamed to the Petition Project, is a duplicitous sham.

If your explanation for a scientific consensus is vast conspiracy, rather than the outcome of the scientific method, you're almost certainly engaged in cognitive dissonance rather than rational thinking.

Scientific consensus is reached through accumulation of peer-reviewed research. It is descriptive, not proscriptive. A scientific consensus is overturned when new research or new interpretations of old research that better fits the observations is presented. It is not refuted by calling it a consensus and conjuring vast conspiracy notions to explain it without acknowledging the accumulated research.

Skepticism isn't just good, it is the basis of science. However, a skeptic can very easily become a denier if the accumulated scientific knowledge conflicts with their preconceived notions and they refuse to update their understanding. "Denier" isn't some sort of ad hominem slight, it is a descriptive term like skeptic. What else should you call somebody who denies knowledge presented to them based on nothing more than belief? Pseudoskeptic is another option.

More reading on climate change is available at:

Examining the Scientific Consensus on Climate Change

(re: John Coleman, the founder of The Weather Channel, says global warming is "the greatest scam in history".)
The Weather Channel Position Statement on Global Warming

Most-Cited Authors on Climate Science: