SoM,
The IPCC emissions scenarios constrain emissions for the main IPCC projections.

However, carbon cycle models are used to look at the impact on the biosphere. These include vegetation models and ocean biogeochemistry models. I don't know much about the results for ocean models. I understand that vegetation is expected to act as a sink CO2 till about 2050 and then start acting as a source.

Steve_M

quote:

I understand that vegetation is expected to act as a sink CO2 till about 2050 and then start acting as a source.

So why should it start to be a source - what causes that?

quote:

So why should it start to be a source - what causes that?

Respiration. Didn't you do any science at school?

quote:

Respiration. Didn't you do any science at school?

Yes - that's where I learnt that vegitation respiration takes in CO2 and expires oxygen.

Ah - that's photosynthesis, by which plants make their food (making sugars and oxygen from water and CO2) during the day when the sun shines.

Then at night-time (and when it's cloudy or in winter), they use the food to respire (with help from oxygen) and give off CO2, water, and energy.

quote:

Then at night-time (and when it's cloudy or in winter), they use the food to respire (with help from oxygen) and give off CO2, water, and energy

And also grow thus fixing carbon etc.

Because at some level plants no longer benefit from increasing CO2, and more warmth causes more carbon to be released from soil:

From:

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model
Peter M. Cox et al Nature 2000

First, vegetation carbon in South America begins to decline, as a drying and warming of Amazonia initiates loss of forest (Fig. 4a). This is driven purely by climate change, as can be seen by comparing the fully coupled run (red lines) to the run without global warming (blue lines). The effects of anthropogenic deforestation on landcover are neglected in both cases. A second critical point is reached at about 2050, when the land biosphere as a whole switches from being a weak sink for CO2 to being a strong source (Fig. 2). The reduction in terrestrial carbon from around 2050 onward is associated with a widespread climate-driven loss of soil carbon (Fig. 4b). An increase in the concentration of atmospheric CO2 alone tends to increase the rate of photosynthesis and thus terrestrial carbon storage, provided that other resources are not limiting4. However, plant maintenance and soil respiration rates both increase with temperature. As a consequence, climate warming (the indirect effect of a CO2 increase) tends to reduce terrestrial carbon storage11, especially in the warmer regions where an increase in temperature is not beneficial for photosynthesis. At low CO2 concentrations the direct effect of CO2 dominates, and both vegetation and soil carbon increase with atmospheric CO2. But as CO2 increases further, terrestrial carbon begins to decrease, because the direct effect of CO2 on photosynthesis saturates but the specific soil respiration rate continues to increase with temperature. The transition between these two regimes occurs abruptly at around 2050 in this experiment ( Fig. 4b). The carbon stored on land decreases by about 170 Gt C from 2000 to 2100, accelerating the rate of atmospheric CO2 increase over this period.

Steve_M

quote:

Because at some level plants no longer benefit from increasing CO2, and more warmth causes more carbon to be released from soil:

From its context the narrative you quote purely looks at land based vegetation. My original question was about algal blooms and the affect they might have in the models.

As far as I understand it, once the sea temperature reaches a certain point, algae stop becoming efficient CO2 sinks.

Looks like quite a lot of Europe is releasing carbon in large quantities at the moment... and the vegetation in this country won't be doing much carbon sinking in the current dreadful weather.

quote:

Originally posted by Steve_M:
Because at some level plants no longer benefit from increasing CO2, and more warmth causes more carbon to be released from soil:

From:

Acceleration of global warming due to carbon-... the rate of atmospheric CO2 increase over this period.

And... Wait for it. Ozone.


Climate Change –
the Costs of Inaction


FROM

Report to Friends of the Earth England, Wales and Northern Ireland
Frank Ackerman and Elizabeth Stanton
Global Development and Environment Institute,
Tufts University
October 11, 2006

QUOTE
However, recent research suggests that even minute increases in ground-level ozone – a pollutant created by fossil fuel combustion – can reduce plant growth. Since increases in CO2 levels, resulting from fossil fuel use, will be accompanied by increases in ozone, some or all of the benefits of CO2 fertilization may be offset by the damages from ozone. This factor has not yet been incorporated into most agricultural forecasts. Additional research is needed to understand the effects on agriculture of joint increases in CO2 and ozone (Long et al. 2006).
UNQUOTE

Minute increases of any already minute amount? That's just great. Just great. Too much ozone we starve - too little we fry. I'm beginning to feel a little trapped.

oh BTW Beeb mentioned ozone today.

http://news.bbc.co.uk/2/hi/science/nature/6916162.stm

Humans and animals produce quite large quantities of methane. I wonder what any further increases in population are going do to...

Also, methane is a cleaner fuel than coal or oil, so maybe we are better off collecting it and burning it before it makes it up into the stratosphere.

In the meantime, I guess we have to stop farting ...

Can someone please explain how methane causes an increase in 'tropospheric ozone'? I'm a bit 'dim' on this one.

OK - The majority of tropospheric ozone formation occurs when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs), such as xylene and methane, react in the atmosphere in the presence of sunlight.

The mods removed my post!!!! All I was doing was quoting a freely available scientific abstract from a prestigious scientific journal - where's the harm in that?

I'll try again - Climate change and trace gases

But then I do wonder how damaging tropospheric ozone can really be if it occurs mostly in urban areas, and is so reactive that it probably just reacts with methane and is destroyed again. Any chemists out there?

Suricat

quote:

Can someone please explain how methane causes an increase in 'tropospheric ozone'? I'm a bit 'dim' on this one.

Methane / Ozone cycle

It's never simple but from my reading although the process starts with some Ozone and with methane as an intermediary in the process one ends up with more ozone than one started with.

This page shows the start of the process:

Sunlight and ozone

Son of Mulder.


Quote.
Methane / Ozone cycle

It's never simple but from my reading although the process starts with some Ozone and with methane as an intermediary in the process one ends up with more ozone than one started with.
EOQ.


In theory these processes only take place in the stratosphere where pressures are low enough for ionic interaction (dry electrochemistry) and solar insolation 'frequencies' are high enough to cause 'molecular cracking' and 'electron ripping'. If this is taking place in the higher pressures of the troposphere, I can only imagine its processes occurring with 'wet electrochemistry'. It requires 'ionic' interaction in solution (usually solutes in water). I don't think methane is soluble in water.

Regards suricat.

Lucibee.


Quote.
This page shows the start of the process:

Sunlight and ozone
EOQ.


Thanks for the link and the quote (I did get to read the post). I think one needs to take care when quoting people on these message boards (don't ask me why). I'm feeling a bit 'left out' now. I've not had a post deleted yet.

Regards, suricat.

realprimate

Increased levels of O3 in the troposphere.

Do you think this could be due to greater employment of the 'lean burn' internal combustion engine, or more lightning flashes? The use of 'cat converters' on vehicles would seem to rule out the car engine's influence, but I don't know about the weather.

Or, would this have anything to do with increased ground insolation of UVb generating a 'dry electrochemistry' effect in the troposphere?

Regards, suricat.

quote:

Originally posted by Lucibee:
Humans and animals produce quite large quantities of methane. I wonder what any further increases in population are going do to...

It's like looking for one missing brick when a whole floor is missing. According to the climate model simulations quoted in my earlier post, Joule heating by electric currents induced by the solar wind is comparable in magnitude with the solar UV absorption, and stronger than the visible light absorption. Yes, it actually heats more than the visible sunlight.

Until this enormous contribution is properly accounted for, I see little use in comparing the weight of grains of sand.

Leo

quote:

Originally posted by suricat:
realprimate

Increased levels of O3 in the troposphere.

Do you think this could be due to greater employment of the 'lean burn' internal combustion engine, or more lightning flashes? The use of 'cat converters' on vehicles would seem to rule out the car engine's influence, but I don't know about the weather.

Or, would this have anything to do with increased ground insolation of UVb generating a 'dry electrochemistry' effect in the troposphere?

Regards, suricat.

Howdo suricat

According to RealClimate
Tropospheric ozone isn't directly emitted by human activity, but is formed in the atmosphere as a result of photolytic reactions related to CH4, CO, NOx and VOCs (Volatile Organic Compounds like isoprene, benzene etc.) - the so-called ozone precursors (chemical products of fossil fuel combustion).

WIKI says that
The main drawback of lean burning is the large amount of NOx being generated, so a complex catalytic converter system is required.
UNQUOTE

Ties-in with what you said. Lean-burn is a newish technology and emission control legislation should keep the lid on things. It looks like climate change will produce more lightning but whether that’s going to generate a significant increase in O3 I don’t know.

Be sad if the ozone hole increases O3 at sealevel.

ttfn

realprimate.

I concur, it would "be sad" is an understatement.

To the best of my knowledge (on an absolute scale) 'almost no O3' is generated by methane within the troposphere. However if it was, the only way I could ever envisage the generation would be by a shorter wavelength (of great amplitude) insolation than normally occurs in the troposphere, or a hitherto unknown chemical reaction!

As for the recent increases of tropospheric O3, I don't see any 'obvious' natural reason for this. Though soil bacteria - or perhaps plankton - changes may be worth investigation. Otherwise, I 'guess' it must be down to a global increase of 'dirty' manufacturing systems causing an increase of NOx and solvent precursors, together with recent forest and heath land fires (natural or unnatural).

One other thought on the tropospheric O3 subject. In the UK since we removed lead (tetraethyl lead) from our motor spirit, we've added a lot more 'benzene' to make it usable in a car engine. Benzene is hard to burn completely and - as you know - is a VOC.

In the meantime, I'll press ahead with hydrogen tec and energy efficiency.

Regards, suricat.

realprimate and Son of Mulder.

My sincere apology! I must correct my last posts here!

Methane is sparingly soluble in water : 100 vols. of water dissolve 5.6 vols. at 0 centigrade, and 3.3 vols. at 20 centigrade (I assume at 1 atmosphere).

There may be some 'wet electrochemistry' with methane in the troposphere!

Regards, suricat.

Leokor

quote:

According to the climate model simulations quoted in my earlier post, Joule heating by electric currents induced by the solar wind is comparable in magnitude with the solar UV absorption, and stronger than the visible light absorption. Yes, it actually heats more than the visible sunlight.

Thanks for all the info on Joule heating. Ive learnt a lot since your first post in this area.

http://www.pmodwrc.ch/eugene1560/sowa/simul.phtml

From this results analysis it's clear how Solar wind interactions are affecting heating in the stratosphere, ozone, zonal flows, polar isolation etc. So it sounds to me that an understanding of the basic physics is there. But for the contribution to temperature forcings at the ground (global warming) it's not clear whether there are changes in the interactions that have contributed to temperature rise over the last 100 years and if so what magnitude of the change (or have I missed something?). ie how much of the 1 WM^-2 is down to Solar wind interaction changes?

Also this looks like another oscillation to add to the many others. And we know that interactions of oscillations can lead to peaks and reson