Stern'i Raporti avalik lahkamine ja globaalsest kliimasoojenemisest

Eelmisel nädalal ilmunud n.n. Stern'i raport sai meedias tugeva järelkaja osaliseks nagu iga apokalüptiline stsenaarium, mis suudab köita ajakirjanike tähelepanu ja motiveerida isegi poliitikuid tegema suurejoonelisi deklaratsioone. Nii võis BBC'st lugeda:

A report by economist Sir Nicholas Stern suggests that global warming could shrink the global economy by 20%.

But taking action now would cost just 1% of global gross domestic product, the 700-page study says.

Tony Blair said the Stern Review showed that scientific evidence of global warming was "overwhelming" and its consequences "disastrous".

Kas Nicholas Stern'i apokalüptilised projektsioonid ka paika peavad on seatud selle nädala jooksul kahtluse alla.

Nii lahkab näiteks Tyler Cowen Sterni raporti mitte kirjandusliku vaid tehnilist poolt, mis seotud diskonteerimismääradega. Cowen toob välja ka kümmekond punkti, mis jätavad tema Sterni raporti suhtes skeptiliseks:

The bottom line: Stern avoids many of the common mistakes in this area. He stresses that a multiplicity of discount rates is required. But his treatment of discount rates is far from transparent and it is in some regards incorrect. That said, the "mistakes" slant the analysis in both directions, rather than confirming any prior that global warming is a significant economic problem.

Robert J. Samuelson võtab sõna Washington Postis, kus lõpetab enda arvamusloo pöörates tähelepanu eeldustele, millest Stern lähtub:

The notion that there's only a modest tension between suppressing greenhouse gases and sustaining economic growth is highly dubious. Stern arrives at his trivial costs -- that mere 1 percent of world gross domestic product in 2050 -- by essentially assuming them. His estimates presume that, with proper policies, technological improvements will automatically reconcile declining emissions with adequate economic growth. This is a heroic leap. To check warming, Stern wants annual emissions 25 percent below current levels by 2050. The IEA projects that economic growth by 2050 would more than double emissions. At present we can't bridge that gap.

The other great distortion in Stern's report involves global warming's effects. No one knows what these might be, because we don't know how much warming might occur, when, where or how easily people might adapt. Stern's horrific specter distills many of the most terrifying guesses, including some imagined for the 22nd century, and implies that they're imminent. The idea is to scare people while reassuring them that policies to avert calamity, if started now, would be fairly easy and inexpensive.

Björn Lomborg lahkab aga üpriski üksikasjalikult kogu raportit tuues välja selle mitmeid puudusi ja probleeme. Väike stiilinäide ka Lomborgi pikemast kirjutisest:

Despite using many good references, the Stern Review on the Economics of Climate Change is selective and its conclusion flawed. Its fear-mongering arguments have been sensationalized, which is ultimately only likely to make the world worse off.

The review correctly points out that climate change is a real problem, and that it is caused by human greenhouse-gas emissions. Little else is right, however, and the report seems hastily put-together, with many sloppy errors. As an example, the cost of hurricanes in the U.S. is said to be both 0.13% of U.S. GDP and 10 times that figure.
. . .
Last weekend in New York, I asked 24 U.N. ambassadors--from nations including China, India and the U.S.--to prioritize the best solutions for the world's greatest challenges, in a project known as Copenhagen Consensus. They looked at what spending money to combat climate change and other major problems could achieve. They found that the world should prioritize the need for better health, nutrition, water, sanitation and education, long before we turn our attention to the costly mitigation of global warning.

We all want a better world. But we must not let ourselves be swept up in making a bad investment, simply because we have been scared by sensationalist headlines.

Lõpetuseks midagi ka Economistilt, mis on jälginud IPCC raportile suunatud kriitikat, mis on isegi parimal juhul puudulik:

One key problem with the IPCC's report, sufficient by itself for Mr Castles and Mr Henderson to declare the document “technically unsound”, is the way the scenario-builders have based their projections of future output on national GDP estimates which have been converted to a common measure using market exchange rates. This procedure leads them to overstate the initial gaps in average incomes between rich and poor countries—because prices tend to be much lower in poor countries. Those gaps are in turn crucial for the IPCC's projections, because the method used in the scenarios assumes not only that the rich countries will continue to get richer but also, in most of the 40 scenarios considered, that the greater part of the (overstated) initial gaps between rich and poor will be closed by the end of the century.

Mida ma kõigi nende tsitaatidega öelda tahan - teadus ei lõppe siis kui saavutatakse konsensus või ilmub 650 leheküljeline raport ja tuleviku ennustamine ning projektsioonide tegemine ei ole teadus.

Ei tasu ka unustada, et globaalse soojenemisega seotud projektsioonid rajanevad mudelitele, kus väga palju oleneb eeldustest ja oletustest ning sellest, mida me praegu teame. Lihtne on siin tuua paralleele majandusteadusega, kus kümmekond pidevalt muutuvat ja eri hetkel erinevat kaalu omavat muutujat võivad muidu stabiilse ja realistliku mudeli jätta mõne aastaga täiesti mõttetuks matemaatiliseks konstruktsiooniks (väikese diskussiooni siin). Nii on näiteks majandusteaduses üpris visalt ignoreeritud ettevõtluse ja ettevõtja rolli, sest statistika ja mudelitega pole siin just eriti palju teha.

Ja lõpetuseks tuletaks meelde veel kord Björn Lomborgi peamist teesi, et ressursid, mis on vajalikud globaalse kliimasoojenemise piiramiseks on sedavõrd ulatuslikud ja tulemused sedavõrd kaheldavad, et palju mõistlikum on need suunata võitluseks konkreetsete probleemidega, millele on juba täna lahendused olemas - puhas vesi, korralik kanalisatsioon, malaariavastased ravimid ja haridus arenguriikdies.