Climate: Growing certainties on warming and human role

Sep 21, 2013

Over the past 23 years, UN scientists have issued progressively stronger assertions about climate change.

They have moved from a sketchy warning that heat-trapping emitted by will cause a "greenhouse" effect to the conviction that this effect is now having an impact on Earth's climate.

Following are extracts from the Intergovernment Panel on Climate Change's assessment reports, the latest of which will be published from Friday.

First Assessment Report (1990)

"... emissions resulting from human activities are substantially increasing of ...

"These increases will enhance the , resulting on average in an additional of the Earth's surface."

Second Assessment Report (1995)

"Most of these studies have detected a significant change and show that the observed is unlikely to be entirely natural in origin...

"... the balance of evidence suggests that there is a discernible human influence on .

"... the average rate of warming [in projections for the 21st century] would probably be greater than any seen in the last 10,000 years, but the actual annual to decadal changes would include considerable natural variability."

Third Assessment Report (2001)

"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.

"... the projected rate of warming is much larger than the observed changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years, based on paleoclimate data."

The report said the global had risen by 0.6 degrees Celsius (1.08 degrees Fahrenheit) between 1901 and 2000.

Human activity was "likely" to be the cause of warming, a term meaning a probability of more than 66 percent.

Fourth Assessment Report (2007)

"Warming of the is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

"Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic [man-made] greenhouse gas concentrations."

The report said that warming over the previous 100 years was 0.74 C (1.33 F), and 11 of the previous 12 years had been the warmest on record.

Human activity was "very likely" the cause of warming, meaning a probability of more than 90 percent.

Fifth Assessment Report (draft version seen by AFP)

"In the northern hemisphere, the period 1983-2012 was very likely the warmest 30-year period of the last 800 years and likely the warmest period of the last 1,400 years.

"....Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5-1.3 C [0.9-2.3 F] over the period 1951-2010."

"...There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level and changed some climate extremes in the second half of the 20th century."

Human activity was "extremely likely" to be the cause of this warming, meaning between 95 and 100 percent probability.

The draft attributes an observed slowing in warming from 1998 to 2012—a phenomenon cited by skeptics as evidence that warming is not man-made—to a temporary cooling cycle in the weather system and lower-than-expected solar activity.

Temperatures since 1901 have risen by 0.89 C (1.6 F), it says.

Additional warming this century is estimated to range from 1.0 to 3.7 C (1.8-6.6 F), and sea level rise from 40 to 62 centimetres (16-24.8 inches), according to four projections based on how much carbon is emitted.

As in past reports, these estimates are an average. Each projection gives a wide margin of variation either side of the figure.

Explore further: Climate report struggles with temperature quirks (Update)

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User comments : 9

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VENDItardE
1.3 / 5 (23) Sep 21, 2013
lies.....and then there are DAMN LIES
TheHealthPhysicist
2.5 / 5 (21) Sep 21, 2013
tards.....and then there are VENDItardsE
Grallen
4.3 / 5 (11) Sep 21, 2013
Hello everyone! Above is a perfect example of paid misdirection. He is persistent to be first to post and post in a way to emphasize a strong emotional reaction. It's all very interesting the methods used in this and other propaganda.

Watching and reading propaganda in action has always been one on my favorite activities. Thank you VENDItardE.

I can recommend various literature on the subject, but my favorite is: Influence: The Psychology of Persuasion: Robert Cialdini. But you can learn a lot from Wikipedia as well. :)
Water_Prophet
1.2 / 5 (19) Sep 21, 2013
Truly man is impacting the world, simply the area in which he inhabits had changed, how could this be otherwise?
Mans' measurement of his impact is still self-serving, his impact on temperature is miniscule compared to the impact on the planet.
In order to use temperature as a yardstick, what are the effects we must account for? Many and non-re-enforcing.
Yet if we look to the water, and its avatars; vapor and ice we see clearly the effects man has upon the world.
The blessed water allows us to see the past, present and future of our effect on the globe. Warming is a scondary effect.
ryggesogn2
1.4 / 5 (19) Sep 22, 2013
Here are real certainties of AGW policies:
"European taxpayers soaked to subsidize high-cost wind and solar power

The German government tried to stem the outflow of investment capital and jobs by making electricity available to aluminum, chemicals, steel and other big energy-intensive German companies at subsidized low rates. Naturally, many more companies began lobbying for those subsidized low rates, and the government expanded eligibility by changing the official definition of "energy-intensive" from those using more than 10 gigawatt-hours annually to those using more than 1 gigawatt-hour annually."
"Airbus is building an aircraft assembly plant in Mobile, Alabama. "
"Siemens is making turbines for fossil fuel power plants in Charlotte, North Carolina."
"BASF has opened a $33 million facility expansion in Research Triangle Park, North Carolina."
"Dow Chemical closed facilities in Belgium, the Netherlands, Spain and the U.K., while opening a plant in Texas."
Forbes.
VENDItardE
1.4 / 5 (20) Sep 22, 2013
Hello everyone! Above is a perfect example of paid misdirection. He is persistent to be first to post and post in a way to emphasize a strong emotional reaction. It's all very interesting the methods used in this and other propaganda.

Watching and reading propaganda in action has always been one on my favorite activities. Thank you VENDItardE.

I can recommend various literature on the subject, but my favorite is: Influence: The Psychology of Persuasion: Robert Cialdini. But you can learn a lot from Wikipedia as well. :)


you truly are a moron and I hope you live for another 10 years so you will realize how stupid you are and never bother the rest of us with your boorish, meaningless comments again.
Neinsense99
2.6 / 5 (17) Sep 22, 2013
lies.....and then there are DAMN LIES


And then there is the smearing with vague innuendo and untestable non-specifics while pretending to occupy a moral high ground.
Gmr
3 / 5 (10) Sep 23, 2013
I don't think he's trying to occupy moral high ground so much as dig out everything around his position to make it seem like higher ground.

He's already picked his ground. Now it's up to him to make sure everyone knows it's higher.
Neinsense99
2 / 5 (11) Sep 24, 2013
I don't think he's trying to occupy moral high ground so much as dig out everything around his position to make it seem like higher ground.

He's already picked his ground. Now it's up to him to make sure everyone knows it's higher.

I did not say he was pretending well.