Is All CO2 Equal? Part 4 - Space Shifting

Following the last part in this series where we looked at times shifting of CO2 offsets (offsetting the CO2 at a different time that it was emitted), in this post we'll look at space shifting, or offsetting the CO2 at a different place than it was emitted.

Dell's program involves planting trees in order to sequester the CO2 due to PC usage. The CO2 emissions will occur at a power plant somewhere near where you're using the PC (although with today's power grids it may not be all that close). Dell's program is in partnership with the Conservation Fund who plants trees throughout the US. Through their overall program they've planted around 5.5M acres (not all of this is for offsetting purposes, though it still helps), 3M in the west, 1M in New England, and the rest in the southeast, midwest and Rocky Mountain region.

At this surface this looks pretty reasonable - sequestration is spread across the same area where emissions are occurring. However, we notice that 60% or so of the emissions are in the west, and only 20% of the US population is there. So this raises an obvious question: can the western US sequester CO2 emitted in the east, midwest and south? Or, more generally, if can we space-shift CO2 offsets? Or (I can't resist) if a tree grows in the forest and there's no emitters around, does it sequester?

I've spent the last couple of weeks looking into this question, and I've come up empty. If someone has done real science on this, please let me know, but I can't even find anyone asking the question.

This question is important to ask. There are reports that trees planted outside of the tropics may not be a net reduction of CO2. There's a bunch of CO2 offset projects which reduce CO2 in developing nations and sell the offsets in developed ones. So in an extreme case, you can ask yourself this: would carbon offsets work if all of the offset projects were in South America and Africa, and all of the credits were sold in North America, Europe and Asia?



It's an interesting question... but the obvious follow-up is, just how much do you think you can offset? The scale of the emissions from any industrial / commercial activity you care to pick will dwarf the amount that can be offset by planting trees. Which is a polite way (hopefully) of saying that at some point you have to move the discussion to reducing emissions, and away from 'accounting tricks'.

Posted by Jon Ellis on February 05, 2007 at 11:26 AM EST #

I don't think the BBC's report of the report is as negative - or complete - as it looks. I think it's journalistic fear mongering: look at my report, it's scary.

I would expect the negative albedo effect of planting trees outside the tropics to be negligible, based on the article: the places that the article says would be most affected are "the seasonally snow-covered regions". If this snow is going away anyway, then we must ask what the environmental impact we want from the surface that is exposed.

The remainder of the world is mostly temperate. The impact of planting trees in areas which have been deforested (such as the english moorlands: forests were cut down for shipbuilding and charcoal for steelmaking, and heather grows incredibly slowly) should be positive, because the albedo change is pretty close to zero.

But if there is an economic leveling effect from rewarding good stewardship of planet - what of it? Isn't that just what we want markets to do?

Posted by Jason Fordham on February 06, 2007 at 06:47 AM EST #

Jon - we'll look at scale in the next post. I don't know the answer yet either. Jason - I'm all in favor of good stewardship, we just need to be clear on what we call it. As this sequence of posts is showing, planting trees is certainly good stewarship, but leaves something to be desired as a CO2 abatement mechanism in upcoming critical years.

Posted by David Douglas on February 10, 2007 at 01:14 PM EST #

Being a curious sort, i did some reading in an attempt to answer your question the effectiveness of 'space shifting'.

CO2 is stable for long periods of time in the atmostsphere, and is therefore distributed evenly around the globe. However, as the majority of the emissions are in the northern hemisphere, and the mixing between the northern and southern hemispheres is slower than the mixing with the northern hemisphere, there is seasonal variation corresponding to the northern hemisphere growing / heating seasons.

You can model all this (seasonal / local / global variability) using this handy NOAA web app.

Posted by Jon Ellis on February 10, 2007 at 06:00 PM EST #

I checked out the data at the site Jon pointed to - it's very interesting. I first took three datapoints: Alert, Nunavut, Canada; equatorial Christmas Island; and the South Pole. These have fairly long runs of data collection, going back to 1985. For each site I customised the graph to use an X range of 1985 to 2010, and a y axis of 300 to 390

Alert shows the strong annual cycle Jon mentions, while at Christmas Island and the South pole the annual cycle is much damped. Looking at the smoothed curves, all three show a rise rate of about 1.6 microMol/Mol/year (average over a 20 year period), and Alert and Christmas Island's smoothed data show that the average concentration of CO2 is about the same at both sites, while the concentration at the South Pole is about 18 months behind the Northern Hemisphere.

Looking also at Tasmania, it seems there's not much variation in the Southern Hemisphere: the graphs is almost identical to the South Pole.

Comparing also the Azores (in the Atlantic) and Midway (Pacific) with eachother and Alert: both ocean sites are lower than the land, and the Atlantic is a little lower than the Pacific.

Interestingly, a comparison of Midway and Hawaii shows that Midway has greater variability, but about the same mean. They're separated by about 10 degrees of latitude. Is latitude, human activity or the winds that are primary?

But the 1.6 gradient appears to be consistent in both hemispheres, which to me says there is mixing, and so space shifting is OK.

Posted by Jason Fordham on February 11, 2007 at 03:38 AM EST #

Doggedly determined to get to the bottom of this...
"The idea that you can go out and plant a tree and help reverse global warming is an appealing, feel-good thing," said Ken Caldeira of the global ecology department at the Carnegie Institution of Washington in Stanford, California, a co-author of the study. "To plant forests to mitigate climate change outside of the tropics is a waste of time."
- Planting trees to save planet is pointless, say ecologists (the referenced paper is probably here...)

My conclusion: planting trees in the tropics might not be a bad idea, but outside of the tropics it is a wash, or potentially even harmful (depending on the albedo of the land being afforested).

Posted by Jon Ellis on February 11, 2007 at 04:54 PM EST #

I've read the paper for the models. They're not much use.

The figures for afforestation are relative to a control model. The control model has "no CO2 emissions for the period 1870–2300".

The afforestation model also "uses the pre-industrial concentrations of CO2 and other greenhouse gases: there is no change in greenhouse gas radiative forcing for the period 1870–2300, and hence there is no CO2-enhanced greenhouse climate change."

This is not what we face. We have a warming world, and the albedo in latitudes greater than 50 degrees will drop as the snow and ice melts. The argument, therefore, that forests at these latitudes have a net negative effect because they have a lower albedo than snow is irrelevant.

The results in the paper "Biogeophysical effects of CO2 fertilization on global climate" simply do not apply to the real world. It solves no real problem.

Posted by Jason Fordham on February 11, 2007 at 07:39 PM EST #

We have a warming world, and the albedo in latitudes greater than 50 degrees will drop as the snow and ice melts. The argument, therefore, that forests at these latitudes have a net negative effect because they have a lower albedo than snow is irrelevant.
I agree with the first part of that. However, if the forest has a higher albedo than the land (grassland / tundra) than it covers the net effect of the afforestation is negative to our warming world.

Regardless, i don't think anyone is proposing to afforest large parts of the 50+ degrees. If trees are going to be planted in a (misguided?) attempt to offset emissions, they may as well be planted in the tropics, where they will have a longer growing season, and can assist in cloud formation.

Posted by Jon Ellis on February 11, 2007 at 09:35 PM EST #

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