2012-03-05 15:26:20The 1990s were not business as usual?
Tom Curtis


I'm just sounding out whether people think this post could be turned into a useful blog post, and rebutal to the myth that the 1990's where business as usual?  I think to do so it needs to be fleshed out with the expectations of Hansen 1988, and also a more explicit comment on the reason for the fall in emissions from Eastern Europe.  If somebody less challenged than me with spread sheets and graphs could do a graph showing IPCC FAR BAU projected forcings, Hansen 88 BAU projected forcings and the actual forcings from NOAA, that would also be a usefull addition, or substitute for the final graph.  It may also be usefull to break up the concentration graph into its four components to allow more detailed discussion. 


Current from is:


Further to GreenCooling @73, this is what the IPCC FAR had to say about their emissions scenarios:

"The scenarios cover the emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorolluorocarbons (CFCs), carbon monoxide (CO) and nitrogen oxides (NOx) from present up to the year 2100. Growth of the economy and population was taken as common for all scenarios. Population was assumed to approach 10.5 billion in the second half of the next century Economic growth was assumed to be 2-3% annually in the coming decade in the OECD countries and 3-5 % in the Eastern Euiopean and developing countries. The economic growth levels were assumed to decrease thereafter. In order to reach the requued targets, levels of technological development and environmental controls were varied."

(Note: The PDF is obviously a scanned document, and scanning has introduced minor spelling and grammatical errors which I have corrected in this and following quotes.)

They go on:

"In the Business-as-Usual Scenario (Scenario A) the energy supply is coal intensive and on the demand side only modest efficiency increases are achieved. Carbon monoxide controls are modest, deforestation continues until the tropical forests are depleted and agricultural emissions of methane and nitrous oxide are uncontrolled. For CFCs the Montreal Protocol is implemented albeit with only partial participation. Note that the aggregation of national projections by IPCC Working Group III gives higher emissions (10-20%) of carbon dioxide and methane by 2025."

Unfortunately, they do not provide either graphs or tables of expected GHG concentrations. It is, however, possible to infer that they expected CO2, CH4 and NOx emissions to increase in line with economic activity based on the fact that they assume no measures to counteract that trend. That is, they expected an annual increase of CO2 (and other GHG)emissions of 2% per annum through the 1990s. That, however, is not what happened:

The very sharp reduction in CO2 emissions in Eastern Europe (light blue on the graph) contrasts starkly with the expected 3% plus economic growth, and presumably emissions growth assumed in the IPCC FAR model. That greatly reduced emissions growth in the 1990's has been followed by above expected emissions growth in the 2000s due to the rapid growth in India and (especially) China. The net effect, however, has been a near linear growth over the two full decades rather than the exponentially increasing growth expected by the IPCC FAR Business As Usual scenario.

A similar pattern is found with NOx, but Methane (CH4) has not only failed to grow as expected, but has flat lined. CFCs are a special case. The IPCC FAR clearly expects some reduction in CFC concentration based on the "partial" implementation of the Montreal Protocol. Implementation of that protocol has been far from partial, however. The resulting reduction in CFC-11 concentrations, and flat lining of CFC-12 concentrations would be a far greater reduction than projected by the IPCC FAR.

The relevant GHG concentrations are shown by NOAA:

The net effect of all these emission reductions has been a significant decrease in GHG forcings relative to 1990 expectations. Total forcings have not even maintained the linear trend from 1978-1990, let alone the ongoing growth expected by the IPCC FAR in the Business As Usual model:

(Radiative Forcing relative to NOAA, modified to show continuation of 1978-1990 trend for comparison. Original image is found here.) 

2012-03-05 16:43:20
Dana Nuccitelli

I think that myth is only relevant in the context of claiming that Hansen 1988 and/or IPCC FAR were wrong because we followed a BAU emissions path.  So the rebuttal should thus be contained within those rebuttals.

I did cover this in a fair amount of detail in Patrick Michaels Continues to Distort Hansen 1988, Part 1 which I then used to update the Advanced rebuttal to "Hansen's 1988 prediction was wrong".  But if you think that could use some more detail, we could update it further, and do a BAU-specific blog post.  I just don't see the need to make a '1990s followed BAU' rebuttal.