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gathering data to test global warming

 

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click to see all the indexGathering data to test global warming is one in a series of briefing documents investigating the indicators, science, analysis and argument surrounding global warming.
One of a grouping of documents on global concerns at abelard.org.
on energy on global warming
On housing and making living systems ecological
sustainable futures briefing documents
Tectonics: tectonic plates - floating on the surface of a cauldron
Index
tracking and measuring global warming is not as easy as cribbage
the complexity of global warming studies
an example of what modern global measurement can do
confusing global and local data
local study over Asia, purporting to be global
now, even nothing to do with the case - trahlah!
on temperature and statistics
another step to understanding antarctica
measuring temperatures - differences in method led to differences in temperature
on temperature and statistics - commentary
the present stage of global temperature measurement
on the fraudulent misuse of statistics by agw deniers
you think ‘the global temperature’ is simple?
computer models

 

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tracking and measuring global warming is not as easy as cribbage

Almost every day, articles and claims are made that this proves or disproves global warming, written or made by people who have not the slightest idea of how complex the studies are. Below, in sections 3 and 4, I refer to two local studies which, as you will see, are being widely confused with ‘global warming’, pro or con.

What is particularly amazing is the incredible dogmatism of the ignorant writers of these items. Yet more examples of the arrogance of ignorance.

The next section gives some idea of the complexity of these studies, both parts being taken from today. Then we have a claim for a localised study in America, this week’s extreme example of the “it ain’t happening” tendency purporting to be global. Next there is an Asia-local example, which makes the contrary claim with the same error.

the complexity of global warming studies

“[...] For a range of sensitivity parameters based on manipulative field experiments, we find a significant suppression of the global land-carbon sink as increases in ozone concentrations affect plant productivity. In consequence, more carbon dioxide accumulates in the atmosphere. We suggest that the resulting indirect radiative forcing by ozone effects on plants could contribute more to global warming than the direct radiative forcing due to tropospheric ozone increases.” [Quoted from nature.com]

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“[...] Many parts of the world already experience near-surface ozone levels greater than 40 parts per billion (ppb)-levels that can injure leaves and reduce crop yields, the researchers note. Ozone levels are projected to increase substantially during the next century to more than 70 ppb above much of the world's land area.” [Quoted from acs.org]

There are also claims around that nitrogen availability will have the reverse effect, and increase carbon uptake by plants.

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Sensing station at Greenland. Credit: David Talbot“One of the wildcards of global warming is how fast the world's massive ice sheets are melting. Efforts to measure the rate of melting on Greenland and Antarctica--and thereby predict how fast sea levels will rise--are complicated by something called "post-glacial rebound" of the earth's crust. When the crust is relieved of its millennia-long burden of ice, it shifts around a bit, and springs back.”

“The stations can detect lateral and vertical changes of the Earth's crust down to the millimeter scale. Equally important, they'll continuously beam out their readings. This data should allow other sensors--which monitor elevation changes, glacial outflow rates, and overall mass of the great ice sheets--to become far more accurate in measuring the rate of ice loss. The international team plans on installing 16 stations in Antarctica later this year as part of the project.” [Quoted from technologyreview.com]

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And here is an example of what modern global measurement can do:

Mid-tropospheric (8km) carbon dioxide. Credit: AIRS Science Team, JPL, NASA
Credit:AIRS Science Team, JPL, NASA

“Although originally designed to measure atmospheric water vapor and temperature for weather forecasting, scientists working with the Atmospheric Infrared Sounder (AIRS) instrument on the NASA Aqua Spacecraft are now using AIRS to observe atmospheric carbon dioxide.[...] The global map of carbon dioxide above [...] shows that despite the high degree of mixing that occurs with carbon dioxide, the regional distribution can still be seen by the time the gases reach the mid troposphere. Climate modelers are currently using the AIRS data to understand the global distribution and transport of carbon dioxide and improve their models.”

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confusing local and global data

The nonsensically titled “Revised Temp Data Reduces Global Warming Fever” is a particularly egregious example from an extremist site.

Note that, in this article, the corrections referred to are only corrections to a USA limited, land level-based series. This is not global. (The USA is 1/50th of the world’s area, so is a ‘local’ planet area.)

Also note that the article is describing how one lot of fudge factors have been replaced by another set, this time called ‘adjustments’.

“[...] replaced by a version of USHCN data with further corrections after an adjustment.”

Map of meteorological observing stations across the 48 contiguous United States. Credit: CDIAC
Map of meteorological observing stations across the 48 contiguous United States.
Credit: CDIAC

The error was picked up by observing the discontinuity in the data, always a red flag that something needs careful checking. In this case, a Y2K error was identified. Despite widespread exaggeration, not only was this an extremely local and not very reliable data series, the correction amounted to approximately one one-hundredth of a degree over the most recent years!

Such corrections are very common. For example, there was an earlier problem where deniers claimed that satellite measurements were not consistent with warming. These claims were found to be in error because the changes in satellite distance had been incorrectly assessed.

This is not ‘exact’ science, but we are gathering better data from year to year, including such corrections as reported here. The consensus remains there is AGW.

Temperature anomalies, gloabal and U.S. Credit:columbia.edu
LOCAL CHANGES ARE NOT GLOBAL WARMING

Note that the USA is anomalous in being relatively warm in both maps, whereas much of the rest of the Earth is strongly warmer. As you can see from the maps, sometimes warmer and cooler areas have moved around, whereas some places, like the Antarctic, are coloured grey for lack of any data over the earlier time period. Unusually, the USA can be seen to have an approximately similar average temperature, while its west coast has cooled and the east coast warmed.

GISS analysis. Credit:
columbia.edu

 

 


 

 

 

 

 

 

 

 

 

 

 


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james hansen on jesters (useful fools) and irresponsible ceos

This 5-page .pdf includes details on NASA US data adjustment and global warming maps.
James Hansen is the Director of the NASA Goddard Institute for Space Studies [GISS].

“The real deal is this: the ‘royalty’ controlling the court, the ones with the power, the ones with the ability to make a difference, with the ability to change our course, the ones who will live in infamy if we pass the tipping points, are the captains of industry, CEOs in fossil fuel companies such as EXXON/Mobil, automobile manufacturers, utilities, all of the leaders who have placed short-term profit above the fate of the planet and the well-being of our children. The court jesters are their jesters, occasionally paid for services, and more substantively supported by the captains’ disinformation campaigns.

“Court jesters serve as a distraction, a distraction from usufruct. Usufruct is the matter that the captains wish to deny, the matter that they do not want their children to know about. They realize that if there is no ‘gorilla’, then usufruct is not an important issue for them. So, with the help of jesters, they deny the existence of the gorilla. There is no danger of melting the Arctic, of destabilizing the West Antarctic ice sheet, of increasing hydrologic extremes, more droughts and stronger forest fires on one hand and heavier downpours and floods on the other, threats to the fresh water supplies of huge numbers of people in different parts of the globe. "Whew! It is lucky that, as our jesters show, these are just imaginary concerns. We captains of industry can continue with business-as-usual, we do not need to face the tough problem of how to maintain profits without destroying our legacy in our children’s eyes." ”

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local study over Asia, purporting to be global

raising more questions than it answers - on brown clouds over asia

“And the haze touches the lower parts of the glaciers in the Himalaya mountain range, said study co-author David Winker, principal investigator of the CALIPSO satellite at NASA's Langley Research Center.

“This suggests that the brown clouds may be contributing to glacial melting in the Himalaya.”

Well, of course it is, some of it will settle on glaciers, thus reducing their albedo. Local air temperatures may also have some effect.

“These particles absorb solar energy and then release it to the surrounding air as heat.”

This sounds like a dubious claim to me (in the context of global warming) as the Earth will shed surplus heat until it returns to natural balance. (See how atmospheric chemistry and physics effects global warming.)

“In contrast, lighter-colored aerosols don't absorb solar energy the way darker particles do.

“These nonabsorbant particles act like a parasol over Earth, reflecting energy back into space [...].” [From page 2 of brown clouds article]

This looks like over-simplification to me, but it is good to see increasing attention to particulates in the atmosphere as this area is insufficiently understood at present.

“ "Our understanding of how air pollution and these brown clouds are influencing climate change is evolving," Samantha said.”

Well, that must be true!

“Averaging the effects of aerosols worldwide masks regional processes that "we need to truly understand when we put all the pieces of the planet together," Pilewskie said.”

Doubtless true, but the soup gets mixed around the world over time and the particulates also steadily fall (precipitate) out. They are also involved in rain formation.

“In 1816 (‘the year without a summer’, attributed to a large volcanic eruption), the world experienced slightly less than a 1.8°F/1°C loss in temperature because of a volcano eruption. During the course of 1816, there was frost in New England in July, worldwide crop failures and many other problems relating to the very small drop in average temperatures. There is more on volcanoes and weather here.” [From Global warming]

This National Geographic article, and the source article in Nature, amount to reporting that is thoroughly confused between global warming and local climate effects.

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now, even nothing to do with the case - trahlah!

And finally, here is a ludicrous report from another extremist site, headed “Global Warming at Odds With Science”. This article, in fact, refers to a 113-page .pdf, which is a review article going through some irrelevant principles of physics and some previous history of warming theory. The article is fine enough for those interested in esoterica. The paper is not peer-reviewed and rather bleats about the inadequacy of computer models, while ironically, it is promoting physics formulae models. That is a most unconvincing personal preference. Warning: I only scanned to page 63 before coming to the conclusion that the paper was of interest, but effectively irrelevant to most contemporary global warming studies and arguments.

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on temperature and statistics

another step to understanding antarctica

“The authors compared recently constructed temperature data sets from Antarctica, based on data from ice cores and ground weather stations, to 20th century simulations from computer models used by scientists to simulate global climate. While the observed Antarctic temperatures rose by about 0.4 degrees Fahrenheit (0.2 degrees Celsius) over the past century, the climate models simulated increases in Antarctic temperatures during the same period of 1.4 degrees F (0.75 degrees C).

“The error appeared to be caused by models overestimating the amount of water vapor in the Antarctic atmosphere, the new study concludes. The reason may have to do with the cold Antarctic atmosphere handling moisture differently than the atmosphere over warmer regions.

“Part of the reason that Antarctica has barely warmed has to do with the ozone hole over the continent. The lack of ozone is chilling the middle and upper atmosphere, altering wind patterns in a way that keeps comparatively warm air from reaching the surface. Unlike the rest of the continent, the Antarctic Peninsula has warmed by several degrees, in part because the winds there are drawing in warmer air from the north. The models generally capture these wind changes, although sometimes incompletely.”

The map and text in the above item are unclear to the point of sloppy. Here is a more secure link from NASA Earth Observatory.

Antarctic Temperature Trend 1982-2004. Credit: NASA image based on data provided by Josefino Comiso, NASA-GSFC
Antarctic Temperature Trend 1982-2004.
Credit: NASA image based on data provided by Josefino Comiso, NASA-GSFC.
Compare with map on Antarctica melting ice, sea levels, water and weather implications

“Cold, snowy, and stuck at the “bottom” of the Earth, Antarctica might seem like a dull place. But this big continent can produce a surprisingly dynamic range of conditions. One example of this range is temperature trends. Although Antarctica warmed around the perimeter from 1982 to 2004, where huge icebergs calved and some ice shelves disintegrated, it cooled closer to the pole.

“This image shows trends in skin temperatures—temperatures from roughly the top millimeter of the land or sea surface—not air temperatures. The data were collected by the Advanced Very High Resolution Radiometer (AVHRR) sensors that were flown on several National Oceanic and Atmospheric Administration (NOAA) satellites. The data come from the AVHRR’s thermal infrared channel—a portion of the light spectrum we can sense as heat but that human eyes cannot see. This image shows temperature trends for the icy continent from 1982 to 2004. Red indicates areas where temperatures generally increased during that period, and blue shows where temperatures predominantly decreased.” [Quoted from NASA Earth Observatory]

related material
antarctica melting ice, sea levels, water and weather implications

 

measuring temperatures - differences in method led to differences in temperature

Temperature variations during the 20th century. Image: Nature
Temperature variations during the 20th century. Image: Nature

“Average global temperatures have steadily risen during the 20th century – the graph of increasing temperature is an image frequently used to illustrate man-made climate change. But the graph does not climb steadily: a number of dips and rises occur over the century.

“One of these, late in 1945, is more pronounced than the others. The cause of the 1945 dip has so far remained a mystery, something highlighted by people who doubt that climate change is caused by human fossil-fuel burning. They say it is proof that burning fossil fuels cannot explain changes in the climate during the 20th century, given that fossil fuels were being burnt throughout.”

“The key, then, is how each nation took its measurements. UK ships tended to throw a bucket overboard and lift it on deck to take the water's temperature. US ships by and large would sample water drawn into the engine room before it was used to cool the machinery.

”Researchers have known for some time that each method has a bias. Temperatures measured in the buckets tend to be lower than those obtained when a thermometer is placed directly into the ocean because heat escapes from it as it is heaved on deck. The type of bucket can influence the temperature as well: wooden buckets, common in the 19th century, offer better insulation than the canvas buckets used in the 20th century. Engine room measurements, on the other hand, tend to be higher than the actual water temperature because these rooms are hot.

“So a temperature record dominated by US measurements in the early 1940s would show the sea surface to be warmer than it actually was at the time.

“Moreover, late in 1945, the UK resumed its measurements and for a period was responsible for half the global record while the US share dropped to 30%. This period is biased towards cooler, bucket-based temperatures, and corresponds to the sudden 1945 dip.”

related material
global warming
anthropogenic global warming, and ocean acidity

 

on temperature and statistics - commentary

It is useful to recognise that there is no such thing as temperature outside of a real-world context. In general, if you put a thermometer into a glass of water, it will register a reading. That reading is due to the amount of energy in the molecules of water bouncing around. If the water is heated, the molecules bounce around more quickly and the increased energy is registered as a ‘rise in temperature’.

Now consider the glass of water. Despite appearances, it does not have a single temperature, but the temperature varies somewhat from place to place in the glass. As the temperature rises, this becomes more apparent, as can be seen in a pan of water roiling as it is boiling. Any temperature measuring device is, in fact, integrating an average measurement over time. This measurement, you may register as accurately as your eyes or measuring devices can discern.

Measuring global temperature is a far more complex process, requiring measurements from all around the world and at many depths - from the top of the atmosphere to deep in the oceans, and even into the Earth. Even this is complicated by the fact that the interior of the Earth also generates heat [see comment at geothermal briefing document].

Choosing the definition for global temperature is no simple task. What statistical weight to do you give to land, to the atmosphere, or to the seas? Almost every day, I see reports confusing global with local temperatures which are, of course, also averages.

'Global cooling' shown as atemporary blip in overall global warming. Image: Keenleyside et al.
‘Global cooling’ shown as a temporary blip in overall global warming. Image: Keenleyside et al.

Recently, I have seen several reports suggesting that La Niña will cause a hiatus in the rises of global temperatures [black line]. However, if you look at the longer-term temperature predictions, you will see that the hiatus [green line] returns to trend line over a few years. In other words, it is not a slowing in global temperature rise, but merely an artefact of the way in which that particular temperature average is being calculated. Note, our measuring sophistication is growing rapidly, as are our technical means of obtaining local temperature samples (in this case, a sample means a single measurement). We now have satellites, ever-improving instrumentation and the means to put sensors in remote places.

It is important to realise that our historic data and temperature surrogates are not as usefully reliable as the latest satellite measurements. There, millions of readings can be taken daily, and the data (and the processing of that data by ever more powerful computers) is of a far higher order than the recordings made by some enthusiast. Such an enthusiast may have lived fifty or a hundred years ago in a city heat island, in a more advanced country, and without having available measurements from the poles, the broad oceans, or darkest Africa.

It is critical to understand that today’s average does not necessarily correspond to an average designed and defined fifty years ago. Notice above, the contrast between the sloppy definitions in the first item, and compare them with the rather better definitions in the second item.

related material
Intelligence: misuse and abuse of statistics

 

the present stage of global temperature measurement

While reading this section, keep always in mind that in climate science (as with all else complex) the system being examined is dynamic. That is, the system, and even the conditions under which it is being measured, are changing as you try to measure it.

  1. “The Intergovernmental Panel on Climate Change (IPCC) in its 4th Assessment Report (AR4) published in 2007 concluded that the warming of the climate system was unequivocal. This conclusion was based not only on the observational temperature record, although this is the key piece of evidence, but on multiple strands of evidence. These factors include: long-term retreat of glaciers in most alpine regions of the world; reductions in the area of the Northern Hemisphere (NH) snow cover during the spring season; reductions in the length of the freeze season in many NH rivers and lakes; reduction in Arctic sea-ice extent in all seasons, but especially in the summer; increases in global average sea level since the 19th century; increases in the heat content of the ocean and warming of temperatures in the lower part of the atmosphere since the late 1950s.

  2. “CRU has also been involved in reconstructions of temperature (primarily for the Northern Hemisphere) from proxy data (non-instrumental sources such as tree rings, ice cores, corals and documentary records). Similar temperature reconstructions have been developed by numerous other groups around the world. The level of uncertainty in this indirect evidence for temperature change is much greater than for the picture of temperature change shown by the instrumental data. But different reconstructions of temperature change over a longer period, produced by different researchers using different methods, show essentially the same picture of highly unusual warmth across the NH during the 20th century. The principal conclusion from these studies (summarized in IPCC AR4) is that the second half of the 20th century was very likely (90% probable) warmer than any other 50-year period in the last 500 years and likely (66% probable) the warmest in the past 1300 years.” [Quoted from uea.ac.uk]

I was once amazed when I asked a very capable botanist what a particular flower was. It looked to me like a typical garden variety. I was told it was a common meadow flower (weed!?). I said it was nothing like the flowers I’d seen under that name - the one in the garden was at least twice as high and the flowers at least two or three times the size

I was informed that the difference was solely down to better soil and fertilisers and attention.

Soil varies over a few feet, the flower had been taken from a nearby flood plain field. Trees a few metres apart can be in very different conditions, let alone on different continents.

This science is about global warming, not the warming in some microclimate in a hollow in the Rockies and another in Siberia.

The graph below has recently [December, 2009] been subject to much uninformed hysteria. What had been ‘hidden’ is data that clearly contradicts the best estimates of the global temperature as measured by satellites and weather stations. It is even possible that the increased ozone levels is slowing growth, as the plants adapt new conditions. There is also some evidence that rain forest trees grow more slowly during warmer periods, while temperate trees seem to grow faster with increasing CO2. Changing rain patterns alters growth rates.[1] And of course, in the meanwhile, evolution will force rapid adaptation under such pressures.

Two versions of Briffa MXD reconstruction, the portion that was deleted from the NOAA archive in red. Source: climateaudit.org
Two versions of Briffa MXD temperature reconstruction, the portion that was deleted from the NOAA archive in red.
Source: climateaudit.org

When reading the two quoted paragraphs above, it is important to attend closely to two factors. In paragraph 1, you will notice that the primary evidence for global warming is real-world [empiric] observations such as retreating glaciers, rising sea levels and, of course, readings from various forms of thermometer.

In paragraph 2, you will see references to various forms of proxy/surrogate such as tree rings (and wood density), ice cores, historic documents and the like. These are secondary sources. It is vital to remember that these sources are usually very local. These sources are used as the best assessments of historic temperatures. All manner of ‘fiddles’ and weightings are applied to this type of data. Attempts are then made to average these sources of data out over the planet. Thus, tree ring data and so on will be sought from many areas, and then averaged according to best judgments/guesses.

In a situation where we believe there to be relevant substantial temperature changes, it is very possible that a local climate may also change considerably over time. Thus, an area with a good growing season may move north or south as the weather systems change. Obviously, we must put much greater store by real temperatures than by guesses and estimates of past conditions divined using proxies.

Remember, more modern actual measurements are best evidence.

Hence, ‘hiding the data’ from a proxy, like tree rings in a local area, and giving preference to real, measured temperatures is the sane thing to do. The manner in which a tree will grow, the width of its rings, the density of its wood, may well change with varying local conditions. Further, the correlations with temperature are merely statistical and not fully modelled in causal terms.

In the next graph, you will notice that each year’s temperature bar estimate [in red] is overlaid by what looks like a long letter ‘I’ [in black].That usually indicates that the probability is that we have a 95% ‘confidence’ that the real temperature fell between the two cross bars of the ‘I’. Notice that as you go further back in time, the range of uncertainty (the upright bar of the ‘I’) increases for obvious reasons.

Sometimes, you will see such ranges of uncertainty indicated by ‘fans’, often giving more than one uncertainty level. This is especially common in graphs giving future forecasts in complex domains, like economics and climatology. [example graph]

NOAA/CRU ocean temperature data. Source: NCDC/NESDIS/NOAA
Ocean temperature data using NOAA (ocean) satellites system,
calibrated by CRU ground-based temperature measurements
(NOAA: National Oceanic and Atmospheric Administration; CRU: Climate Research Unit]

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on the fraudulent misuse of statistics by agw deniers

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you think ‘the global temperature’ is simple?

The system of ARGO probes is only recently active. They measure ocean temperature by duck diving, and then radio to satellite their GPS position and the local water temperature.

The system involves 3000 points, with 5 levels going down progressively to 200 metres.

The oceans are over 70% of the planetary surface that’s around 335 million sq kms. This means there is one measurement point for every 100,000 sq kms.

Meanwhile, ice is pouring into the oceans at an increasing rate. this is even expected to effect the Atlantic Conveyor. The Atlantic Conveyor is a vast overturning current involving much deeper depths, possibly slowing and increasing the cold in the Atlantic.

At the same time, the present La Niña is expected to cool some surface areas temporarily.

 

computer models

You will hear people claiming that predictions of future temperature are ‘just computer models’. I hope by now that you will realise that they are no such thing. The forecasts are based on the best real data we have available this week, supplemented, as we go back in time, by ever more unreliable guesswork.

A lot of the arithmetic for analysing and forecasting weather patterns was worked out in the early 20th century, but at that time, it took weeks of hand calculation to forecast just one day ahead. With the coming of computers, we can do far more calculations far more quickly. Hence, the increasing sophistication and reliability of weather forecasting. However, we can still only forecast a very few days ahead in the generality, and less so the finer the detail we seek, like for example the Cockermouth flood of autumn 2009, or a more general system such as Cyclone Klaus. And as always, we are dealing with forecasts, not hindsight.

While we do not need such fine detail for long-term climate change, the methods used are very similar. As you see from the example above of the new oceanic survey measuring system, the cells being used are very large/crude.

There is no ‘complete’ climate computer model. To gain one, you would need to measure cells down to the micro-level, not every 100,000 sq km - and still it would not be ‘complete’. So we do the best we can. At present, we simply do not have computers powerful enough to do useful modelling for the whole climate, even with our crude 100,000 sq km cells. We have to model parts of the climate and them attempt to meld them together. Hence, the continual requests for ever bigger and more expensive computers by the world’s prime climate research centres.

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end notes

  1. As with everything else in this complicated world, things are not so simple as this. The searches for species and areas, where the trees tend to vary primarily by one critical variable, mean that obtaining suitable samples for tracking temperature is not straightforward.

    For example, in the American South-West the limiting factor is rainfall, not temperature. This makes the sampling pretty well useless as a check on global warming. In Alaska, the critical factor is temperature but, of course, Alaska is one of the areas where the temperature is changing fastest, leading to invasions by beetles and disease, as well as changing soil conditions as the perma-frost melts.

    Thus while the changing ring size is an excellent method of dating, it is not nearly so reliable for AGW studies.

  2. weighting
    In other words, what is considered a more reliable source of data will be given more weight than data thought to be less reliable.



  3. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the ±1 standard deviation range of individual model annual averages.
    The orange line is for the experiment where concentrations were held constant at year 2000 values.
    The grey bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the grey bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints.

    Notice carefully how the line narrows to a single point at about the year 2000. This is our present day best estimate. Notice also how the fans spread as they go both forwards and backwards [in grey] in time, with our past estimate and with our future forecasts becoming more and more uncertain the more distant the time.

  4. la niña and el niño
    “La Niña is associated with cooler than normal water temperatures in the Equatorial Pacific Ocean, unlike El Niño which is associated with warmer than normal water.”
    source: NOAA

  5. After the end of the first World War, a British meteorologist - Lewis Richardson [1881-1953] - worked out that it is possible to use mathematical calculations to predict future weather conditions, because the atmosphere follows the laws of physics. However, the real-world weather would arrive before Richardson had finished doing the very complicated calculations, using weather readings only taken at six hourly intervals.

    Later, when computers were available, Richardson’s lengthy calculations could be done more quickly. The complex numerical weather model that was built incorporated the known physical laws for regulating weather. The Earth’s surface is divided into a grid. Above each grid square is a portion of the atmosphere, called a box. Within each box, atmospheric wind, air pressure, temperature and humidity observations are recorded at 20 different altitude levels.

    A computer then analyses the data, received from the more than 3,500 observation stations world-wide, from which is produced a rolling 15-minute world weather forecast. This is then repeated until a six-day world forecast is created in 15 minutes.

    And forecasting accuracy? For instance, the UK Meteorological Office currently claim an 86 % accuracy for 24-hour forecasts, and 80 % accuracy for 5-day forecasts. [2009]

  6. Even the 100,000 sq km cells in the ocean only apply to the ocean and its top 200 m. Full climate models would have to reach from the top of the atmosphere down to the ocean depths. They would have to take into account the arrangements of the tectonic plates/continents, land heights, albedos, weather and oceanic circulation systems, and much else. Eventually, the behaviour of the sun, as well as the nuclear reactor at the centre of the Earth, would need to be included.



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graph from the Summary for IPCC4 report