How to Talk to a Climate Skeptic: Responses to the most common skeptical arguments on global warming A Grist Special Series

‘Natural emissions dwarf human emissions’—But emissions are only one side of the equation 5

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: According to the IPCC, 150 billion tonnes of carbon go into the atmosphere from natural processes every year. This is almost 30 times the amount of carbon humans emit. What difference can we make?

Answer: It's true that natural fluxes in the carbon cycle are much larger than anthropogenic emissions. But for roughly the last 10,000 years, until the industrial revolution, every gigatonne of carbon going into the atmosphere was balanced by one coming out.

What humans have done is alter one side of this cycle. We put approximately 6 gigatonnes of carbon into the air but, unlike nature, we are not taking any out.

Thankfully, nature is compensating in part for our emissions, because only about half the CO2 we emit stays in the air. Nevertheless, since we began burning fossil fuels in earnest over 150 years ago, the atmospheric concentration that was relatively stable for the previous several thousand years has now risen by over 35%.

So whatever the total amounts going in and out "naturally," humans have clearly upset the balance and significantly altered an important part of the climate system.

Former musician, turned tree planter, turned software engineer. Same old story…

I have been blogging about climate change since 2006 at A Few Things Ill Considered.

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  1. winterfrost Posted 6:48 am
    02 Aug 2007

    Natural compensation?Can you please explain the comment about nature compensating for part of the emissions so "only about half of the CO2 we emit stays in the air"?  Through what mechanism(s) is this happening?  Does this mean that humans are emitting a net 3 gigatonnes of CO2 which is not handled, or is it already included in the 6 gigatonne figure?  Thanks!

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  2. Delay And Deny's avatar

    Delay And Deny Posted 4:53 pm
    02 Sep 2007

    Dat Don't Look Like That Chart, Boss!

    What humans have done is alter one side of this cycle. We put approximately 6 gigatonnes of carbon into the air but, unlike nature, we are not taking any out.
    Wait a minute.   If that's the case, then, as you say, it should take us 30 years to double the total CO2 in the atmosphere.
    But Al Gore showed a graph with an exponential growth rate in a few years?!

    John Bailo


    Sutext:

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  3. gzuckier Posted 3:24 am
    06 Nov 2007

    Natural compensation?That's just straight math from observed numbers. We know pretty much how much carbon we have burned since the beginning of the industrial era (270 Gton of carbon); which leads to knowing how much carbon dioxide we have added to the atmosphere (270 Gton of carbon). We know how much the carbon dioxide in the atmosphere has actually increased: (160 Gton of carbon). It therefore must be that natural sinks have absorbed 110 Gton of carbon in the past 200 years, over and above the pre-industrial source/sink balance. Exactly which natural sinks have sucked up the excess carbon is still a matter of debate, but the amount is determined by the math.
    In fact, the IPCC model, to be conservative with respect to human effects, assumes that there has also been an increase in natural sources, at present unknown, of carbon dioxide of equal magnitude to human sources over the same period (i.e. another 270 Gtons of carbon over the preindustrial amount), which in turn mathematically requires that presently unknown natural sinks have absorbed an additional 380 Gton of carbon, or 120% of what humans have produced, more than their preindustrial amount.
    If in fact these presently unknown sources do not exist or are smaller, then the effect of human activity must be larger than the IPCC estimates. Of course, if they are larger than assumed, then the effect of human activity will be smaller; but it's increasingly unlikely that such large unknown natural sources of carbon dioxide exist, particularly ones that have increased their activity in parallel with human output, by coincidence.

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  4. airplanesocks Posted 10:37 am
    10 May 2008

    Missing carbonThe comment about nature compensating for part of our emissions could refer to two different things: the recycling effect of the biosphere (photosynthesizers) or the missing carbon  phenomenon.  The biosphere is a major carbon sink and a carbon reservoir-- the ocean and forests both take up carbon for photosynthesis (plankton in the ocean are very busy). However, the biosphere is calibrated, if you will, for a carbon cycle that doesn't involve massive emissions from stored carbon resources (fossil fuels),  so it isn't really equipped to handle extra carbon.

    Since we have a good idea of how much carbon we've emitted since the Industrial Revolution (money makes people keep records), we have a pretty good idea of how much carbon ought to be in the atmosphere right now--and it isn't there. There is no certain answer at this point about where the carbon actually is; there are only three places that it can be hiding logically.  The ocean; the terrestrial biosphere; or the atmosphere (and we know it's not there).

    The greenhouse effect is causing a 'greening' at higher latitudes--plants that couldn't survive at high latitudes because of colder temperatures are now able to move there because the temperatures are right for them--but that is unlikely to draw down enough CO2 on its own to offset that 7 Gt per year of anthropogenic CO2 emissions.  The ocean has a much faster turnover rate for CO2, so a number of people think that it might be there, as a dissolved gas.

    In short, we know we're emitting about 7 Gt of CO2 per year (about 6 Gt in fossil fuel burning, and 1 Gt from deforestation),  but only 3.5 Gt appears to stay in the atmosphere.

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  5. megal Posted 6:51 pm
    12 Oct 2008

    RE: The SOA with reach: Web-Oriented Architectureswf to avi converter can convert SWF files to various audio videos like SWF to MP3 Converter, SWF to AAC Converter, SWF to WMA Converter, etc.

    Permalink

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Series Intro
'There is no evidence' -- Yes, there is 59
'Mauna Loa is a volcano' -- CO2 rise is measured on top of a volcano! 8
'Warming is due to the Urban Heat Island effect' -- No, it isn't 25
'One hundred years is not enough'--Yes it is 18
'The scientists aren't even sure' -- No scientist ever is 33
'One record year is not global warming'--Luckily, there are plenty more years to consider 19
'Glaciers have always grown and receded'--A few glaciers melting does not mean global warming 14
'The temperature record is unreliable'--But temperature trends are clear and widely corroborated 8
'It's cold today in Wagga Wagga'--Weather and climate are different 2
'The satellites show cooling'--No, they don't 15
'What about mid-century cooling?'--No one said CO2 is the only climate influence 11
'Antarctic ice is growing'--Well, probably not, but even if it were, we are not off the hook 8
'Global warming stopped in 1998'--Only if you flagrantly cherry pick 170
'But the glaciers are not melting'--Except ... they are! 3
'Antarctic sea ice is increasing'--Yes, but ... 14
'Sea level in the Arctic is falling'--Sea level is a surprisingly complicated thing 11
'Climate sensitivity is not very high'--Thermal inertia of the oceans means the jury is still out 2
'Some sites show cooling'--But you can't draw global conclusions from individual sites 0
'Global warming is a hoax'--I wish James Inhofe were just a hoax ... 12
'There is no consensus'--If this is not consensus, what would consensus look like? 109
'Position statements hide debate'--True enough, but that is not the whole picture 5
'Consensus is collusion'--Is climate science maturing, or should we reach for our tinfoil hats? 8
'Peiser refuted Oreskes'--In a poor piece of work that has been retracted by its author 4
'Models don't account for clouds'--Clouds are complex and uncertain, but unlikely to stop warming 6
'Climate models are unproven'--Actually, GCM's have many confirmed successes under their belts 13
'Aerosols should mean more warming in the south'--More North. Hemisphere warming is well-understood 1
'We can't even predict the weather next week'--But weather is not climate 11
'Chaotic systems are not predictable'--Sure, but who says climate is chaotic? 13
Understanding what is happening right under our noses does not require paleoclimate perfection 1
'They predicted global cooling in the 70s'--But that didn't even remotely resemble today's consensus 29
'Hansen has been wrong before'--Maybe, but not about the climate! 13
'It was warmer during the Holocene Climatic Optimum'--This period was not global and not like today 4
'The Medieval Warm Period was just as warm as today'--Repeating this point does not make it true 216
'Greenland used to be green'--Don't judge a book by its cover, much less a land by its name 23
Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago 5
'The hockey stick is broken'--Well, no ... but who's playing hockey anyway? 6
'Vineland was full of grapes'--Or was it an early advertising campaign? 4
'Global warming is part of a natural cycle'--This idea is one short step above appealing to magic 39
'Mars and Pluto are warming too'--No they aren't -- and what if they were? 24
'Volcanoes emit more CO2 than humans'--Not even close ... 31
'The null hypothesis says warming is natural'--An inappropriate test, and one that would fail anyway 4
'Climate is always changing'--That doesn't mean it isn't different today 5
'Natural emissions dwarf human emissions'--But emissions are only one side of the equation 5
'The CO2 rise is natural'--No skeptical argument has been more definitively disproven 12
'We are just recovering from the LIA'--Why should we expect this to happen? 4
'Climate scientists dodge the subject of water vapor'--No, they really don't 4
Water vapor is indeed a powerful greenhouse gas, but there is plenty of room for CO2 to play a role 29
There is no proof in science, but there are mountains of evidence 78
'CO2 doesn't lead, it lags'--Turns out CO2 rise is both a cause and an effect of warming 43
'Geological history does not support CO2's importance'--Just not true 0
'Historically, CO2 never caused temperature change'--Not so 19
'It's the sun, stupid'--Very bright, yes, but not getting brighter 18
The problem is not how high the temperature may go, but how fast it is changing 14
'Kyoto is a big effort for almost nothing'--Kyoto is only in its first phase 16
China and India have joined Kyoto, they just have different obligations, as is morally appropriate 3
'Climate change mitigation would lead to disaster'--Not really, but this may be lesser of two evils 6
Only if you ignore fossil fuel emissions 10
In 2008, did temperatures drop as much as they rose over the whole 20th century? 71
Is the IPCC so wrong their theories contradict a basic laws of physics? 23
Is the American Physical Society a crack in the climate change consensus? 3
Summer ice in the Arctic has recovered--Was the Arctic ice retreat a climate anomaly? 7
'Global warming comes from within'--Is heat at the Earth's core the real cause of global warming? 10
Was there another breathless announcement of another phony record, and another quiet retraction? 1
Hansen wants the skeptics thrown in jail--Did James Hansen really want to try the climate skeptics? 6
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