Thursday, April 15, 2010

Eli can retire Part IX - PPP, MER, GDP AEIOU

From the US EPA responses to challenges to its Endangerment Finding for increasing CO2 concentrations, something economical

Comment (4-44):
A commenter (4632) objects to the emission scenarios produced by the IPCC because of critiques by Castles and Henderson (2003a, 2003b, 2005) that highlight the use of market exchange rates (not purchasing power parity) and the implausible assumption that poor nations will equalize per capita emissions with rich nations.

Response (4-44):
Both IPCC (2007) and CCSP (2007b) address the issue of using market exchange rate (MER) versus purchasing power parity (PPP) approaches in determining future gross domestic product (GDP) growth rates, in response to the critiques by Castles and Henderson (2003a, 2003b, 2005). The IPCC (Fisher et al., 2007) states the following:

In the debate on the use of exchange rates, market exchange rates (MER) or purchasing power parities (PPP), evidence from the limited number of new PPP-based studies indicates that the choice of metric for gross domestic product (GDP), MER or PPP, does not appreciably affect the projected emissions, when metrics are used consistently. The differences, if any, are small compared to the uncertainties caused by assumptions on other parameters, e.g. technological change (high agreement, much evidence).

The IPCC adds the caveat that, unlike emissions, the numerical expression of GDP does depend on conversion methods. CCSP (2007b) notes that while MER is used to set the base year of the models in that assessment, “growth prospects and other parameters for the world’s economies were assessed relative to their own historical performance” in order to avoid potential issues arising from interactions between the MER/PPP issue and assumptions regarding convergence.

While we find that both the IPCC and CCSP approaches yield credible estimates of future emissions that have been well supported by the literature, the robustness of conclusions based on emission projections developed through different means adds even more confidence that the TSD is appropriately summarizing the best existing science


jyyh said...

TSD? Are they saying emmissions are going to be what they're going to be irrespective of GEP (Gross Earthly Product) and calculation method (co-operative black receipts or accountant-based double-book)? Sorry, it's the spring.

Alastair said...

It is impossible to produce emission scenarios that are beyond reproach, so there will always be scope for sceptics to criticise them. Let's face it - "Prediction is very hard, especially about the future" - Yogi Berra.

Although "the implausible assumption that poor nations will equalize per capita emissions with rich nations" does seem unlikely, it is equally implausible that the rich nations will continue to grow at historical rates now that oil and other natural resources have begun to run out.

But surely these scenarios are being produced to show what could, not will, happen. So a worst case should be included, even if it is inevitably used by some people as an excuse to bury their heads in the sand.

Horatio Algeranon said...

If the recent flurry of posts is any indication, retiring can be tiring.

EliRabett said...

Copy and paste
Copy and paste
Let no one else's work
Go to waste

Sit in the chair
Sit in the chair
Drinking your coffee
Combing your hare

carrot eater said...

anybody have an idea whether all this volcanic ash will be a forcing worth talking about?

Anonymous said...

apparently it didn't get it up to the stratosphere. Should settle relatively quickly and do not impact climate that much.


EliRabett said...

To the same point, is this thing gonna go blooey? Too lazy to try and track it down when there are so many smart people posting here

Connor a.k.a bit_pattern said...

You're a Funny Bunny, Eli. Much love.