Klima å sånn

Det viser seg at jeg har venner som mener at menneskeskapte klimaforandringer er en myte.

OK, jeg er allergisk mot hype og har en sterk ryggmargsrefleks mot å ta konvensjonell visdom for god fisk. Og jeg mener at å diskutere klimaforandringer er litt som å sitte inne i et brennende hus og diskutere om røyking er farlig eller ikke. Og organisasjoner som Greenpeace, Bellona og Zero ser jeg på først og fremst som politiske opportunister; mange av medlemmene mener godt, men de er fullstendig ukritiske mhp de fikse ideene sine... fikse ideer som går tiår tilbake, og i mange tilfeller nå er avlegs.

Men det betyr ikke at de tar feil i alt; ei heller betyr det at den riktige responsen er å starte en like virkelighetsfjern sekt med motsatt fortegn.

Klimaprognosen alle snakker om er IPCC sin. Jeg har selv kritisert den for å ikke ta PO med i beregningen (Aleklett nevner det samme i videoen jeg linket til forrige dagen). Jeg har ikke studert den i detalj - den er lang og tung, og jeg mener som sagt gjentatte ganger at vi har langt alvorligere problemer som også er nærmere i tid... men nå har jeg i alle fall lest FAQen deres. Men la oss begynne med begynnelsen, hva er IPCC egentlig?

Her er en beskrivelse fra IPCCer Professor Martin Parry:

The IPCC is not, as some believe, a group of scientists, but a panel set up by the United Nations comprising representatives from about 140 governments to consider what we currently know about climate change.

The panel decides whether an assessment is needed, and then engages scientists to conduct it.

Since its establishment in 1987, there have been four such major assessments, published roughly every five years (1990, 1995, 2001 and 2007), sprinkled with occasional special reports on specific topics.

Why this government role? The reason is because governments need a sound summary of knowledge which, once commissioned and adopted, becomes accepted by them.

This is why the IPCC assessments are so significant; they represent the description of knowledge that governments "buy into".

We should not expect them to be full of exciting new material; rather, they are consolidations of what we know.

This is why they err, if anything, on the side of conservatism and have been criticised for not exploring the outer edges of knowledge.

En gjennomlesing av IPCCs FAQ gir et veldig tillitvekkende inntrykk. For eksempel var en hovedinnvending at IPCC undervurderer totalt/overser variasjoner i Solas intensitet... etter å ha lest hva IPCC selv skriver virker dette veldig rart; de snakker ganske mye om Sola. For eksempel,

Solar output has increased gradually in the industrial era, causing a small positive radiative forcing (see Figure 2). This is in addition to the cyclic changes in solar radiation that follow an 11-year cycle. Solar energy directly heats the climate system and can also affect the atmospheric abundance of some greenhouse gases, such as stratospheric ozone

(her)

... men det er ikke ukontroversielt, som RealClimate innrømmer:

The solar influence on climate is a controversial topic in climate research (see previous posts here and here). The irradiance changes are assumed to be relatively small and the importance of potential amplifying mechanisms is still a matter of current debate. One reason for these uncertainties is that there are only approximately 25 years of satellite-based observations of the solar irradiance. Sunspot observations for the last 400 years clearly indicate that current levels of solar activity are very different from the state of the sun during the Maunder minimum (from approx. 1645 to 1715 AD) where almost no sunspots could be observed.
[...]
Therefore, in the view of the uncertainties and the conflicting data it doesn’t seem to be appropriate to make uncritical and sensational claims about the history of the sun. As long as the differences between the ¹⁰Be records are not understood, conclusions based on only one of these records should be treated with caution. Atmospheric ¹⁴C concentrations, on the other hand, are much less sensitive to a climate influence during the last 1000 years and, therefore, can provide good estimates of the history of the sun. However, the disagreement between ¹⁴C-based solar activity and group sunspot number (Muscheler et al., 2005) should remind us that the variations of the solar activity are not yet completely understood.

Regardless of any discussion about solar irradiance in past centuries, the sunspot record and neutron monitor data (which can be compared with radionuclide records) show that solar activity has not increased since the 1950s and is therefore unlikely to be able to explain the recent warming.

(fra Did the Sun hit record highs over the last few decades?)

New Scientist har også en fin oversikt: Climate change: A guide for the perplexed (se også Climate is too complex for accurate predictions)

NS tar for seg snakkepunktet "men det var varmere i middelalderen" her; angående viking-jordbruk på Grønland linker de til ‘Greenland used to be green’—Don’t judge a book by its cover, much less a land by its name (grist).

Og Scientific American spør Just How Sensitive Is Earth's Climate to Atmospheric Carbon Dioxide? og får svaret

Earth scientist Aradhna Tripati of the University of California, Los Angeles's Department of Earth and Space Sciences and her colleagues extracted a record of past atmospheric concentrations of CO2 stretching back 20 million years from the shells of tiny creatures known as foraminifera buried in a column of ocean mud and rock. The microscopic animals build shells of calcium carbonate out of minerals in seawater—a process that is affected by the water's relative pH (acidity), which is, in turn controlled by the level of CO2 in the atmosphere. More CO2 in the atmosphere means a more acidic ocean.

"The two species we picked to analyze [Globigerinoides ruber and G. sacculifer] are both ones that are around today, and the living animals actually have photosynthetic algae as symbionts, which means that they live in the surface ocean, since the algae require sunlight to survive," Tripati explains. And that means the fossil record of their shells will reveal the relative acidity of the surface waters in the ratio of boron to calcium as well as the specific chemical signature of the boron itself. "When seawater is more acidic, less boron gets incorporated into the calcium carbonate shells," she adds.

The researchers first matched this fossil record secured by the Integrated Ocean Drilling Program Expedition in the western tropical Pacific to existing records from bubbles trapped in Antarctic ice cores that stretch back 800,000 years, which preserve a precise record of past atmospheric composition. Thus reassured of the technique's accuracy, they plunged back into deep geologic time.

"Modern-day levels of carbon dioxide were last reached about 15 million years ago," Tripati says, when sea levels were at least 25 meters higher and temperatures were at least 3 degrees C warmer on average. "During the middle Miocene, an [epoch] in Earth's history when carbon dioxide levels were sustained at values similar to what they are today [330 to 500 ppm], the planet was much warmer, sea level was higher, there was substantially less ice at the poles, and the distribution of rainfall was very different."

Further, "at no time in the last 20 million years have levels of carbon dioxide increased as rapidly as at present," Tripati adds; CO2 concentrations have climbed from 280 ppm to 387 ppm in the past 200 years. And "our work indicates that moderate changes in carbon dioxide levels of 100 to 200 parts per million were associated with major climate transitions and large changes in temperature"—indicative of a very sensitive climate.

Jeg mener selv jeg har en god nese for bullshit; ingenting av det jeg har sett på her lukter. Ja, det er mye de ikke vet, ja, prognosene er forbundet med stor usikkerhet; men alt tyder på at det dreier seg om seriøse forskere som gjør sitt beste for å få oversikt over et uoversiktlig problem. Jeg tror på prof. Parry når han sier at "they err, if anything, on the side of conservatism".

Risikoen er på nedsiden.