Four degree rise will end vegetation 'carbon sink'

Dec 16, 2013

Latest climate and biosphere modelling suggests that the length of time carbon remains in vegetation during the global carbon cycle - known as 'residence time' - is the key "uncertainty" in predicting how Earth's terrestrial plant life - and consequently almost all life - will respond to higher CO2 levels and global warming, say researchers.

Carbon will spend increasingly less time in vegetation as the negative impacts of take their toll through factors such as increased drought levels - with rapidly released back into the atmosphere where it will continue to add to global warming.

Researchers say that extensive modelling shows a four degree temperature rise will be the threshold beyond which CO2 will start to increase more rapidly, as natural carbon 'sinks' of global vegetation become "saturated" and unable to sequester any more CO2 from the Earth's atmosphere.

They call for a "change in research priorities" away from the broad-stroke production of plants and towards carbon 'residence time' - which is little understood - and the interaction of different kinds of vegetation in ecosystems such as carbon sinks.

Carbon sinks are natural systems that drain and store CO2 from the atmosphere, with vegetation providing many of the key sinks that help chemically balance the world - such as the Amazon rainforest and the vast, circumpolar Boreal forest.

As the world continues to warm, consequent events such as Boreal forest fires and mid-latitude droughts will release increasing amounts of carbon into the atmosphere - pushing temperatures ever higher.

Initially, higher atmospheric CO2 will encourage plant growth as more CO2 stimulates photosynthesis, say researchers. But the impact of a warmer world through drought will start to negate this natural balance until it reaches a saturation point.

The modelling shows that global warming of four degrees will result in Earth's vegetation becoming "dominated" by negative impacts - such as 'moisture stress', when plant cells have too little water - on a global scale.

Carbon-filled vegetation 'sinks' will likely become saturated at this point, they say, flat-lining further absorption of atmospheric CO2. Without such major natural CO2 drains, atmospheric carbon will start to increase more rapidly - driving further climate change.

The researchers say that, in light of the new evidence, scientific focus must shift away from productivity outputs - the generation of biological material - and towards the "mechanistic levels" of vegetation function, such as how plant populations interact and how different types of photosyntheses will react to temperature escalation.

Particular attention needs to be paid to the varying rates of carbon 'residence time' across the spectrum of flora in major carbon sinks - and how this impacts the "carbon turnover", they say.

The Cambridge research, led by Dr Andrew Friend from the University's Department of Geography, is part of the 'Inter-Sectoral Impact Model Intercomparison Project' (ISI-MIP) - a unique community-driven effort to bring research on climate change impacts to a new level, with the first wave of research published today in a special issue of the journal Proceedings of the National Academy of Sciences.

"Global vegetation contains large carbon reserves that are vulnerable to climate change, and so will determine future atmospheric CO2," said Friend, lead author of this paper. "The impacts of climate on vegetation will affect biodiversity and ecosystem status around the world."

"This work pulls together all the latest understanding of climate change and its impacts on global vegetation - it really captures our understanding at the global level."

The ISI-MIP team used seven global vegetation models, including Hybrid - the model that Friend has been honing for fifteen years - and the latest IPCC (Intergovernmental Panel on Climate Change) modelling. These were run exhaustively using supercomputers - including Cambridge's own Darwin computer, which can easily accomplish overnight what would take a PC months - to create simulations of future scenarios:

"We use data to work out the mathematics of how the plant grows - how it photosynthesises, takes-up carbon and nitrogen, competes with other plants, and is affected by soil nutrients and water - and we do this for different vegetation types," explained Friend.

"The whole of the land surface is understood in 2,500 km2 portions. We then input real climate data up to the present and look at what might happen every 30 minutes right up until 2099."

While there are differences in the outcomes of some of the models, most concur that the amount of time carbon lingers in vegetation is the key issue, and that of four degrees or more - currently predicted by the end of this century - marks the point at which carbon in vegetation reaches capacity.

"In heatwaves, ecosystems can emit more CO2 than they absorb from the atmosphere," said Friend. "We saw this in the 2003 European heatwave when temperatures rose six degrees above average - and the amount of CO2 produced was sufficient to reverse the effect of four years of net ecosystem carbon sequestration."

For Friend, this research should feed into policy: "To make policy you need to understand the impact of decisions.

"The idea here is to understand at what point the increase in global temperature starts to have serious effects across all the sectors, so that policy makers can weigh up impacts of allowing emissions to go above a certain level, and what mitigation strategies are necessary."

Explore further: Scientists identify most pressing environmental issues posed by pharmaceuticals

More information: Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2, www.pnas.org/cgi/doi/10.1073/pnas.1222477110

Related Stories

Plants can change greenhouse gas emissions after warming

Aug 21, 2013

(Phys.org) —Different moorland plants, particularly heather and cotton grass, can strongly influence climate warming effects on greenhouse gas emissions, researchers from Lancaster University, The University ...

Peering through the global carbon cycle

Aug 21, 2013

The oceans are one of the sink absorbing carbon dioxide derived from human activity. Yet fully quantifying the ocean's carbon uptake under a changing climate remains challenging.

High CO2 spurs wetlands to absorb more carbon

Jul 16, 2013

(Phys.org) —Under elevated carbon dioxide levels, wetland plants can absorb up to 32 percent more carbon than they do at current levels, according to a 19-year study published in Global Change Biology from t ...

Recommended for you

Report IDs 'major weaknesses' at nuclear-arms lab

14 hours ago

One of the nation's premier nuclear weapons laboratories is being called out by the inspector general of the U.S. Department of Energy for "major weaknesses" in the way it packaged contaminated waste before shipping it to ...

User comments : 28

Adjust slider to filter visible comments by rank

Display comments: newest first

ubavontuba
2.4 / 5 (14) Dec 16, 2013
Idiots. Do these people ever even bother to look at real data?

Historically, a warmer world is a greener world. And ecosystems don't suffer from CO2 "saturation." More CO2 fertilizer = more growth. Even the deserts are greening.

jsolebello
1 / 5 (2) Dec 16, 2013
Should the title of this article have read "Four degree rise will end vegetation's 'carbon sink'"?
Drjsa_oba
3.7 / 5 (6) Dec 16, 2013
In my Naivety I thought 'residence time' was already taken into account whenever I saw reference to Carbon Sinks. Hence there can only be so much carbon sequestration per hectare depending on vegetation type and cover level. Naturally the climate effects both those factors to varying degrees -- as does mans horticultural activities.
JIm Steele Landscapes and Cycles
2.8 / 5 (13) Dec 16, 2013
During the Little Ice Age trees stopped growing in many places around the northern hemisphere. The warming since 1850 has enhanced the vegetation by all accounts. But in the world of make you own models anything goes and unlike science that where such speculation needs to be tested, these predictions are so far into the future it takes decades to debunk It amazing that such fear mongering has now been labeled science
eric_in_chicago
3.3 / 5 (12) Dec 16, 2013
wow, yeah, trees grow ten feet per minute on the surface of the sun. in fact, they CAUSE sunspots and pollution, just like president raygun said.

yep, all desserts are lush and fur-tiled!
Kron
2.5 / 5 (11) Dec 16, 2013
all deserts are lush and fur-tiled.

Deserts are dry places. Their temperatures are irrelevant. You know that cold deserts exist, don't you, dumb-dumb? An increase in mean temperature on Earth will result in an increase of vegetation (as long as the temperatures stay under waters BP temp.) Global warming will cause minimizing of desert areas, (just as can already be seen with satellite images).
24volts
4.1 / 5 (7) Dec 16, 2013
I keep reading about how there will be less rain as the average temperature goes up but quite honestly that doesn't make sense to me and the reason is the higher the air and water temps go the more water will evaporate into the atmosphere. That water has to come back down as rain or snow somewhere as the atmosphere mixes due to trade winds, etc... Weather patterns may be changing so that various areas are getting dryer and wetter than before but where is all the extra going to go? Some areas may be going to get a lot more rain than they used to.
Kron
2.2 / 5 (10) Dec 16, 2013
Should the predictions by climate scientists come to fruition, the changes will bear a net positive biosphere change. The thing is, though, anthropogenic (man caused) global warming is insignificant. Most of the temp change in the last 100 years (which isn't much mind you, less than a degree Celsius) has been a natural recovery of the Earth since the mini ice age.
Kron
1.2 / 5 (10) Dec 16, 2013
Weather (fluid dynamics) are affected by temperature, the higher the temp the more dynamic the weather. If you pay attention to world weather events, you'll notice an increase of severity and incidence of storms. This is heat dispersement. Weather rebalances the climate.
Kron
1.9 / 5 (9) Dec 16, 2013
Climate science has long ago ventured into the land of fairytales.

... Man-bear-pig is real people! He's half man, half bear, half pig. He's coming, you'll all see!
Maggnus
3.7 / 5 (9) Dec 16, 2013
Hi Jim. back for a bit I see! Sock-puppetry will probably get you in trouble.

You say vegetation has been enhanced since 1850. Can you show any support for this proposition?

I think you're being awfully cynical, albeit no doubt that's your intent. Predictions have their place, as long as the starting conditions are well explained and logical. There's no need to throw the baby out with the bathwater.
Maggnus
3.7 / 5 (9) Dec 16, 2013
Ah Kron, back sharing your misunderstandings again I see!

24-volt, other than saying there will be less rain, you've got it mostly right actually. There will be less rain days, perhaps, but more rain in each event. Warmer air does hold more moisture. The problem is that the higher moisture extent causes more rain in the individual storms, while also causing there to be a lower number of storms. So areas will have longer drought-like periods followed by massive rains when the rain does come.

Or so the predictions go. Jim Steele is right about one thing - notwithstanding the robustness of the science behind the predictions, the reality is that the climate is incredibly complex. So while the predictions have been more correct then incorrect, they haven't been perfect, a fact denialists love to seize on in their mantra against human-caused global warming.
Kron
2.1 / 5 (10) Dec 16, 2013
How about the misunderstandings of the climatologists who programmed the modeling software in use today. The earth radiates far more into space (in the infrared wavelength especially) than the 'garbage in' suggests. This is why the 'garbage out' is so grossly exaggerated, the reason all predictions to date have been way off. GIGO. When the temp of the Earth goes up, it becomes brighter in infrared when viewed from space. Why is that, exactly? The 'heat trap' ain't as much of a trap as the climate panel 'prophets' claim it to be.

An increase in heat equals increase in water vapor and increase in weather. Rain combines with co2 to produce carbonic acid. Co2 is literally washed out of the atmosphere and excess heat is dispersed and radiated away.

When models don't match up with the physical world, they're wrong. This AGW alarmism is a crock of shit. Humans have minimal influence in climate, and the changes we make are short lived.
Maggnus
3.7 / 5 (9) Dec 17, 2013
Well Kron, there are so many misunderstandings in your post that its hard to even know where to start. You clearly don't understand modelling nor climatology, you seem to have no grasp of how radiative forcing works, and your parroting of the denialist blogs you read just makes you sound shrill.

Here. start with this: http://hero.epa.g...id=92936
alfie_null
3 / 5 (6) Dec 17, 2013
How about the misunderstandings of the climatologists who programmed the modeling software in use today.

All seven models got it wrong. All the folks involved in all these efforts missed it, but you didn't. Sorry, what's your background?

Perhaps they are all stupid and you aren't.

Or maybe they all conspire? Against you!

When models don't match up with the physical world, they're wrong. This AGW alarmism is a crock of shit. Humans have minimal influence in climate, and the changes we make are short lived.

I know a "krok" when I see one.
runrig
3 / 5 (6) Dec 17, 2013

Deserts are dry places. Their temperatures are irrelevant. You know that cold deserts exist, don't you, dumb-dumb? An increase in mean temperature on Earth will result in an increase of vegetation (as long as the temperatures stay under waters BP temp.) Global warming will cause minimizing of desert areas, (just as can already be seen with satellite images).


Aridity is very relevant. Some deniers seem to think that all that will happen in a warming world is that the same "weather" will occur but that it's just going to be a little warmer on average. Err – no, it's not that simple. It is a function of the D-K syndrome that things can be so simplified in the mind such that the application of this simple-headed-ness leads to black/white answers. Does it not occur to you that nothing in the world works that way.
The whole point of GW is that rainfall will be pushed to greater extremes of flood/aridity
All the CO2 plant-food in the world will not make things grow without water.

runrig
4 / 5 (5) Dec 17, 2013
I keep reading about how there will be less rain as the average temperature goes up but quite honestly that doesn't make sense to me and the reason is the higher the air and water temps go the more water will evaporate into the atmosphere. That water has to come back down as rain or snow somewhere as the atmosphere mixes due to trade winds, etc... Weather patterns may be changing so that various areas are getting dryer and wetter than before but where is all the extra going to go? Some areas may be going to get a lot more rain than they used to.


Well done - right on the button.
runrig
3.4 / 5 (5) Dec 17, 2013
Weather (fluid dynamics) are affected by temperature, the higher the temp the more dynamic the weather. If you pay attention to world weather events, you'll notice an increase of severity and incidence of storms. This is heat dispersement. Weather rebalances the climate.


"Weather rebalances the climate." Unfortunately it doesn't – can't do. What it does is TRY to rebalance the climate.
Weather cannot return the excess heat being retained by GHG's any quicker – that is a radiative process not conductive/convective.
The Earth is no longer in radiative balance – the weather overlies that fundamental - it cannot alter it.
Weather is "internal chaotic noise" and no more.
Just as boiling water in a pan churning around (weather) makes no difference to the time taken and energy used to get that water to 100C (given known initial conditions). Just basic physics.
runrig
3.4 / 5 (5) Dec 17, 2013
How about the misunderstandings of the climatologists who programmed the modeling software in use today. The earth radiates far more into space (in the infrared wavelength especially) than the 'garbage in' suggests. This is why the 'garbage out' is so grossly exaggerated, the reason all predictions to date have been way off. GIGO. When the temp of the Earth goes up, it becomes brighter in infrared when viewed from space. Why is that, exactly? The 'heat trap' ain't as much of a trap as the climate panel 'prophets' claim it to be.


As Maggnus has said evidence of this "garbage in/out" would aid your argument – otherwise it is just hand-waving.... and bollocks.
You need a lesson in radiative physics my friend.
The Earth becomes brighter because by S-B it has to radiate at a higher temp to rectify the radiative imbalance it has in Solar absorbed – IR emitted.

http://en.wikiped...mann_law
Energy emitted is proportional to T^4
Comprede now?
runrig
3.4 / 5 (5) Dec 17, 2013
An increase in heat equals increase in water vapor and increase in weather. Rain combines with co2 to produce carbonic acid. Co2 is literally washed out of the atmosphere and excess heat is dispersed and radiated away.

When models don't match up with the physical world, they're wrong. This AGW alarmism is a crock of shit. Humans have minimal influence in climate, and the changes we make are short lived.


Crickey you're full of it – Bollocks, that is.

Awake up and smell the roses my friend.
You'll need to climb out of your rabbit-hole first though.
Kron
2.6 / 5 (5) Dec 17, 2013
evidence of this "garbage in/out" would [help]

http://www.mdpi.c...1603/pdf
runrig
3.4 / 5 (5) Dec 17, 2013
evidence of this "garbage in/out" would [help]

http://www.mdpi.c...1603/pdf


I don't usually link to a site that would "offend" a denialist, but I will this time as you link to a paper by a denialist climatologist (one of the 3% ). For it shows the shortcomings of the paper – and it seems there are many - like not dealing with atmospheric and climate science, and not getting an adequate peer review.

http://www.skepti...ack.html

Understand the S-B law now Kron?
Maggnus
3.7 / 5 (6) Dec 17, 2013
Really kron, Roy Spencer again?
Spencer is a signatory to An Evangelical Declaration on Global Warming, which states that "Earth and its ecosystems – created by God's intelligent design and infinite power and sustained by His faithful providence – are robust, resilient, self-regulating, and self-correcting". He believes that most climate change is natural in origin, the result of long-term changes in the Earth's albedo and that anthropogenic greenhouse gas emissions have caused some warming, but that its warming influence is small compared to natural, internal, chaotic fluctuations in global average cloud cover.
Maggnus
3.7 / 5 (6) Dec 17, 2013
More about Spencer:
In the early 1990s, Spencer and John Christy published a few papers looking at the discrepancy of satellite measurements of temperature in the troposphere versus surface warming. This was an important problem in climatology and, since then, there has been voluminous literature published on the topic. The consistent finding has been that the discrepancy was due to instrumental error in the satellite measurements and some methodological problems in Spencer and Christy's work. Further adjustment has reduced the disparity to be in line with models.
Maggnus
3.7 / 5 (6) Dec 17, 2013
And for a really close look at Spencer and his claims: http://www.skepti...ncer.htm

You talk about garbage input kron, then hold Spencer's poorly researched and disproved paper up as an example of how it should be? Can you say "hypocrisy"?
Kron
2 / 5 (4) Dec 17, 2013
I'm talking of nothing but data. The energy in vs the energy out. The data speaks for itself. An increase of heat results in fluid dynamics and is consequently more radiative through which heat is released into space. The data speaks for itself.
Maggnus
3.4 / 5 (5) Dec 17, 2013
I'm talking of nothing but data. The energy in vs the energy out. The data speaks for itself. An increase of heat results in fluid dynamics and is consequently more radiative through which heat is released into space. The data speaks for itself.


Talk about the data: http://www.john-d...cing.htm

http://www.slf.ch..._GRL.pdf

http://www.grida....r-06.pdf

You're not very good at this denial thing are you kron? Perhaps you should take a few months and learn about this thing you are trying to deny.
runrig
3.4 / 5 (5) Dec 17, 2013
I'm talking of nothing but data. The energy in vs the energy out. The data speaks for itself. An increase of heat results in fluid dynamics and is consequently more radiative through which heat is released into space. The data speaks for itself.


It certainly does Kron - but not in the way you want.

"The data speaks for itself. An increase of heat results in fluid dynamics and is consequently more radiative through which heat is released into space."

Err - you'll have to put that past me one more time. Gobbledygook as it stands.