Life in the skin of a bubble
Around our planet wraps an exquisitely thin film of air and water, inside which exists all the life we know. The planet is eight thousand miles wide, the film of air and water is just a few miles thick, and outside it is the cold vacuum of space.
    Conditions in the life-supporting film have rather suddenly started changing. The air is heating, and the ocean is acidifying.
    Both trends are caused by increasing quantity of carbon dioxide gas in the atmosphere. That extra gas is being pumped into the atmosphere by us.

Temperature
These are the estimates by climate scientists (based on many kinds of measurement) for the global air temperature, the average temperature of the atmosphere above all lands and seas. (In degrees Celsius; to convert to Fahrenheit, multiply by 1.8 and add 32.) A seemingly small difference such as 0.1° C implies a vast amount of extra heat in the air.

13.6°: approximate level in 1850.
13.66°: mean for 1850 to 1899.
13.75°: same for 1900 to 1960.
13.97°: same for the 30-year period 1961-1990 (usually quoted as roughly 14°, and being used as a baseline for many figures now given).
14.24°: same for the decade 1990-1999.
14.42°: same for 2000-2008. (About 0.75° above the 19th-century level.)
15.6° (about 2° above the 19th-century level): the highest possibly safe point, or more realistically the tipping point which it would be folly to reach: global temperature at which there would be a 50-50 chance of preventing runaway heating. Others (such as the governments of several nations already harmed by rising oceans) would rather set this safe limit 0.5° lower.
20° (6° or 7° above the 19th-century level): probable level reached in the 21st century if present trends (middle estimate) continue.

This is a graph by years from 1850 to 2008. Actually it shows not the absolute temperatures (which I think easier to understand) but the “anomaly”or difference from the 1961-1990 average. The black curve is for the mathematically “smoothed”values.

Graphs like this show a general trend, but also many smaller-scale up-and-down jags, due to secondary factors, such as volcanic eruptions, which can cause cold years by putting dust into the upper atmosphere.

These are the 20 hottest years of the more than a century and a half on record.

1998 14.546°
2005 14.482°
2003 14.473°
2002 14.464°
2004 14.447°
2006 14.422°
2001 14.409°
2007 14.405°
1997 14.351°
2008 14.325°
1999 14.296°
1995 14.275°
2000 14.270°
1990 14.254°
1991 14.212°
1988 14.180°
1987 14.179°
1983 14.177°
1994 14.171°
1996 14.137°

It is striking that these include every year from 1994 onward. And not one from before 1983.

Acid in the ocean
The graph of global heating has been going up in step with the graph of atmospheric carbon dioxide, though roughly, because jags in the graph are caused by lesser factors, such as volcanos and world wars. So there is room for some argument about the details.
    But the graph of ocean acidity goes up exactly in step with the increasing carbon dioxide. It has to. Carbon dioxide in contact with water dissolves into it and forms carbonic acid. More carbon dioxide, more carbonic acid. We know how much more carbon dioxide gas we are generating, we can predict how much more acidity that will cause, we can measure the pH (acidity) of the oceans, and it keeps to prediction.
    There is no room for argument about it. And so there is no room for valid doubt about the whole linked pattern. Human activity has reached a scale at which it is corroding the thin film in which we, and other creatures, live.
    Increasing acidity prevents calcium carbonate from forming in the water. Calcium carbonate is used to make the shells of corals, molluscs, and plankton. Plankton are the base of the marine food-chain. Coral reefs, the "rainforest of the ocean", cover only one percent of ocean area but support a quarter of all ocean species, and they are already being destroyed by human activity such as fishing with dynamite, as well as by warming water. If the acid in the oceans keeps increasing at its present rate, it will not only hinder formation of calcium carbonate but dissolve it. Alarmingly large areas of coral reefs have already gone white, as dead as bones.
    (Actually ocean acidity goes up somewhat faster than aerial carbon dioxide: rivers add the acid rain caused by power plants; they also add fertilizer runoff from farms, which cause algal blooms, which decay into carbon dioxide directly in the water.)

Is there now a change to cooling?
Some say that since there was a peak in 1998 the planet must have reverted to a cooling trend. But this is an instance of a shorter-term jag. There are two oceanic phenomena, called “El Niño”and “La Niña”, that add to or subtract from the general trend. They bring warm and cool currents, respectively, to the eastern Pacific and have world-wide effects on weather. The 1998 El Niño was the strongest on record and added to global heating. It was followed by a La Niña that brought some cooling. Another El Niño began in mid 2009 and will probably continue at least into early 2010.
    Even though this El Niño is far weaker than the 1998 one, 2010 will probably exceed the 1998 record and be the hottest year ever recorded: 14.58° C. This is the prediction (Dec. 10, 2009) of the United Kingdom's Met Office, which gives it a more than 90% probability, not a certainty, because the El Niño could end sooner or volcanic eruptions could have their usual cooling effect.

It's cold here! — where's Global Warming when we need it?
The January 2010 temperatures were well below normal in most of the USA, the British Isles, Scandinavia, and especially northern Russia and Siberia.
    But they were well above normal in most of Europe, central Asia, North Africa, the Middle East, and Canada. (Vancouver had its warmest January ever, so that snow had to be trucked and helicoptered in for the winter Olympics.) This is an instance of deceptive local variation. Globally, this January was the second warmest on record.

Ice and snow
Glaciers in many parts of the world have been retreating, the Greenland and Antarctic ice sheets are shrinking. The winter ice cover on the Arctic Ocean is becoming smaller year by year — threatening the survival of polar bears. White ice reflects the sun's heat back into space whereas dark water absorbs it, thus increasing the heating and the melting — an obvious feedback loop.
    Ice and snow on the Himalayas ars rapidly dwindling. Photographs of mountain ranges taken in 1968 and 2007 show glaciers shrunken and the snow line hundreds of feet higher. The glaciers of the Himalayas are the sources of the great rivers that supply water to the Indian subcontinent, southeast Asia, and China — an enormous fraction of the world's population.
    In Ladakh (“Little Tibet”, the northernmost part of India) most farmers depend on runoff water from glaciers. Average temperatures have risen by 1C in winter and 5C in summer from 1973 to 2008, less snow falls and it disappears more quickly, so glaciers and irrigation water are disappearing. A local engineer has been meeting a little of the farmers' desperation by making “artificial glaciers” (in winter the water in some pipes is allowed to keep running, though not needed, to stop it from freezing; instead he lets it out through holes to freeze on north-facing hillsides, thus saving it for the summer).

Mistake on page 493
The Intergovernmental Panel on Climate Change was set up by the United Nations in 1988 to evaluate research done around the world, mainly using peer-reviewed articles in the scientific literature, and from 1990 onward it has published four massive reports and many supplementary ones.
    But it's all nonsense! It includes a mistake.
    On page 493 of the 976 pages of the second of the four volumes (totaling more than 3000 pages) of the IPCC's Fourth Assessment Report, 2007, there is an estimate that Himalayan glaciers are melting fast enough to disappear by 2035. This estimate, based on information from the World Wildlife Fund about difficult measurements of these debris-strewn glaciers, was soon retracted, by the IPCC and by the WWF. It had been caught by Professor Graham Cogley of Trent University in Ontario, who said: "The reality in the Himalayas is bad enough without exaggerating it. The glaciers are losing mass and we are fairly sure they are losing mass faster now than a few years ago. We also know that the Himalayan glacier water could become a non-renewable resource."
    The mis-estimate was seized on by global-heating deniers and labeled "Glaciergate" — as if it will be fine for the glaciers to disappear and the Ganges, Mekong, and Yangtze to run dry a few decades later.
    And there is at least one other mistake: the percentage of the Netherlands below sea-level was said to be 55; this figure, which had been provided by the Dutch government, should have been 26, as the IPCC and the Dutch government soon stated.
    And there have been mistakes in the opposite direction. IPCC reports have given estimates for the speed of disappearance of Greenland and Antarctic glaciers and the Arctic ice cap, and the rise of sea levels, which are proving to be too low. Deniers avoid mentioning this.
    In many thousand pages of carefully detailed science, it would be surprising if there were not a mistake. To say that it invalidates the whole and shows that global heating is not happening is like saying a car won't run because someone left a speck of dirt on the right rear window. Or, to use another's metaphor (Luke 6:42): "Hypocrite, first remove the beam from your own eye, and then you will see clearly to remove the speck from your brother's eye."

A conspiracy — on which side?
Much of the solid research used by the IPCC was done by the three or four researchers of the Climatic Research Unit of the University of East Anglia, at Norwich, directed from 1998 by Professor Phil Jones. The CRU became bombarded with questions from the public. I didn't know this when I sent a question, to which I got a courteous reply. Many of the questions were hostile and "makework" — designed to waste the scientists' time — and provoked some natural impatience, which the scientists expressed in emails to each other. Hackers broke into the CRU's computers, stole hundreds of private emails, and selectively leaked them to the internet — timing this for the eve of the December 2009 Copenhagen Climate Conference, with obvious intent to cripple it.
    The stolen and misrepresented emails were trumpeted as "Climategate", the uncovering of a conspiracy among climate scientists to withhold evidence against their conclusions. It did play a large part in the failure of Copenhagen. Phil Jones admitted that he contemplated suicide.
    Who were the real conspirators? They remain — unlike the scientists they boobytrapped — in hiding. (There has been a suggestion that they worked, like other hackers, from Russia.) No one has a love for climate disaster, a motive to pretend that it is looming; there are certainly those who have a vested interest in pretending that it isn't.
     An inquiry by the cross-party Science and Technology Select Committee of the House of Commons reported in March 2010 that there was no case against Jones for him to answer, and that he should return to the post from which he had stepped down. In April another investigation, by an independent panel of leading professors from the US, Britain, and Switzerland, chaired by Lord Oxburgh, rector of the Imperial College London, utterly exonerated the scientists. " . . . absolutely no evidence of any impropriety anywhere . . .  all of the conclusions were honest and sensibly arrived at . . .  the work has been carried out with integrity, and allegations of deliberate misrepresentation and unjustified selection of data are not valid . . .  no hint of tailoring results to a particular agenda . . .  We saw no hint of deliberate scientific malpractice in any of the work of the CRU . . . " One of the investigators, Prof. David Hand, commented:"There is no evidence at all of anything underhand, the opposite if anything, in that they have brought out in the open the uncertainties associated with what they are doing." The CRU scored, as it were, 98 out of 100; the slight criticisms by these investigators were that the CRU could have used some more recent statistical methods, and that climate scientists in general should be a bit more willing to release masses of their primary data, even to those obviously demanding it in hope of undermining their work.
    "Hackergate" has uncovered the sneakery to which anti-scientists will stoop. It has done nothing to discredit the huge body of evidence that global heating is real and is human-caused.

Geo-engineering
Some suggest that, because we are failing to stave off disaster by curbing carbon emissions, we should turn to drastic technologies:
   —Reduce the sun's in-coming energy by lofting into the atmosphere mirrors, or sulfate particles, or salt crystals from the sea, which would cause brighter clouds to form
     —Or fertilize the ocean with iron in the hope that it will absorb carbon dioxide faster.
    —Or (probably the most hopeful) extract carbon dioxide from the atmosphere, and store it underground or use it for fuel.
   The first problem is the “law of unintended consequences”. Thus the salt-crystal-spraying idea was regarded as the most promising, until in 2010 scientists found it could actually have the opposite effect by interfering with natural processes.
    However, if these methods led to some disaster they could be discontinued. But that raises the second and greater problem. Any such method would all too likely divert attention, funding, and research away from solving the root problem. Emissions would continue, there would be an even greater quantity of carbon dioxide in the atmosphere, and if the geo-engineering effort failed, or was not maintained, heating would suddenly resume at an overwhelmingly increased rate.

The successful precedent: the ozone "hole"
Life on earth is shielded from most of the sun's ultraviolet radiation by an ozone-containing layer at a height of around 20,000 feet. (Ozone molecules are made of three oxygen atoms; there is one ozone molecule to about 100,000 other molecules in the surrounding air.)
    Industrial chemicals, especially halons and the chlorofluorocarbons used in refrigerators and spray cans, rise and destroy the ozone. That this was happening became suddenly clear in 1985 when laborious measurements made by three researchers at the British Antarctic Survey's Halley station showed that over Antarctica, where special conditions in spring hurry the process, ozone had thinned by 40 percent in a decade. The discovery nearly didn't happen: the Conservative government of Mrs. Thatcher was busy cutting funds for science like this.
    Scared by the prospect of blinding eye cataracts and fatal skin cancers, the world agreed in 1987 to the Montreal Protocol, which would phase out ozone-destroying chemicals. By 2009 all UN members had signed, and production of those chemicals has dropped by 95 percent. The "ozone hole", which had looked like spreading across the world, has not gone away, nor have the ozone-destroying gases, but they have leveled off and the layer may recover by 2100. Unfortunately the chemicals and some of those used to replace them are also greenhouse gases, up to 10,000 times more so than carbon dioxide.
    Still, the Montreal Protocol has been called "the most successful international environmental agreement". It shows that we can do it.

Some readings

—Text of an article from a region where global heating is starkly visible. The permafrost across Siberia and northern North America is thawing and releasing huge jets of methane (25 times more effective as a greenhouse gas than carbon dioxide). Look at the plea in the last paragraph.

—Text of an article from just after the shamefully feeble end of the Copenhagen summit climate conference, calling for citizen action.

—Text of an article about a transformation of our way of raising food, which would have advantages for the natural world and would reduce carbon dioxide emission, if only it could be adopted quickly and widely.