> “When the greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilization from the added carbon dioxide in the atmosphere, leading to more leaf growth in northern forests, for instance. Now, with the MODIS data that lets us understand the phenomenon at really small scales, we see that humans are also contributing.”
That global warming may induce more agriculture, and forest growth, in the global North is something I'd like to learn more about. Anyone have any further reading to recommend?
It is well known that CO2 improves plants growth. It is also well known that plants grow better within a narrow band of temperatures.
Increasing both the CO2 contents of the atmosphere and Earth's temperature will have some complex results where on the places within that temperature band, plants grow slightly faster, on places that cross from too cold into the band plants grow much faster, and on places that cross from that band into too hot plants will grow much slower.
Also, solar incidence has a much larger effect than CO2 concentration, so the places with best growth rate can only cross into the too hot region, and polar places crossing into the good temperatures can't really compensate (besides, there isn't much area at the polar regions, unless you are talking about the hole Antarctic getting green).
And, anyway, water availability has a much larger effect than solar incidence, and this one is completely chaotic. So, good luck getting any conclusion.
Temperature is chaotic, but with a large predictable component. Except for black swans, a computer model can get on the ballpark, and the climatology people have many of them.
The specifics of how trees react to increase CO2 concentration varies from one species to the other. AFAIK, only a few species have been measured, thus the increase on rate of growth on that component is quite uncertain. That can be improved by empirical tests, that many specializations of science are currently working into. Of course, the big elephant in the room here is ocean plankton, that has a two sided relation with CO2, because it both participates on photosynthesis and increases ocean acidity. AFAIK, there is little known on how those react.
Solar incidence is completely predictable, and doesn't tell a good story for global warming.
And for humidity, I don't think there is any reliable model out there. None of those are my specialization, so I may be wrong, but I don't think we have anything nearly viable for predicting this one.
Yes, and then the model will give you some result, but you will never know if you are accurately accounting for reality in all its complexity. The more complex your model, the less likely you are to match reality precisely. To quote a cliche, the model is the map, not the territory.
It's kind of an obvious implication to there being more CO2 in the atmosphere. Plants like it. If it gets warmer at higher latitudes, there will also be more plants able to grow there.
There was a 200 page report on global warming from the 1980s on HN a few days ago which had several sections on this as upsides to global warming. I only read 50 pages of it, but it is a remarkably clear and level headed document.
One serious caveat about the "plants like more CO2" idea:
The increase in CO2 strongly disfavors slow-growing old groth and established ecosystems, and favors fast growing plants, which are typically invasive species that take over and destroy established ecosystems, and reduce biodiversity.
In particular I'm interested agricultural and dense growth projections in the North (and South?). The above stuff covers this only in passing to my recollection.
Okay, here's the thing: If you have plants with more or less CO2 under otherwise the same conditions you'll have more growth in the plants.
However that's not how the planet works. If you put more CO2 in the atmosphere you'll have for example rising sealevels and larger deserts (and probably more effects that diminish food production). You can't just pick a single effect of increased CO2 in isolation. (Except of course that's what the CO2 coalition does, because they chose to believe fairytales instead of science on climate change.)
ELI5: how will melting ice caps cause rising sea levels? Ice has higher volume than water it's made of, so the effect of ice melting should be sea level falling. At least that's the case of Arctic Sea, which is just this: frozen sea. Antarctic is different, because most of the ice is located on land, above the sea level. But then, shouldn't northern cap melting cancel out melting of the south one?
For floating ice, the mass of the ice is buoyantly supported by displacement of an equal mass of liquid water. As the SI units for mass were originally defined by the density of liquid water at STP, of 1 g/mL, when the ice melts, it supplies exactly as much volume as was previously displaced, so there is no change in level.
As it happens, seawater is denser than pure water, with a density averaging 1.088 g/mL, so if we were just talking about floating ice, 1 kg of floating ice would displace 1 kg of seawater, with a volume of 0.919 L, when the ice (mostly-pure water) melts, it supplies additional volume of 1 L, an increase of 8.8% over the submerged volume of the ice. This mixes with the saltwater to reduce salinity and lower the density, but the overall effect is a slight rise in water level.
Now forget about floating ice. Some ice is not floating. It rests upon surface rock. When it melts, 100% of its volume (eventually) flows down into the ocean. When land-ice melts, it has a far greater impact on sea level. But we only need to worry about land ice that rarely melts due to seasonal variation: ice found mainly in the glaciers and icepack on Greenland and Antarctica. Due to albedo and insulation effects, it is more difficult to melt land-ice than sea-ice, but it is indeed melting at rates unprecedented within the relatively short span of human observations.
(If a land-ice glacier calves an iceberg into the ocean, the immediate effect is to raise sea level by about 86% of the volume of the ice, with additional rise occurring as the ice melts.)
Even if the poles were modeled as just ice cubes floating on water, then melting them would not decrease the sea level, as 1/12th volume of the ice would be above water. So even with this very simple model the South Pole has no way to compensate the north pole’s contribution.
I can appreciate the idea, but this attitude is why bullshit pervades.
If a person or group consistently advances bullshit, it eventually becomes a useful heuristic to dismiss that person's or group's ideas without consideration.
It takes more energy to argue against the bullshit than it does to advance it in the first place, so insisting on that argument hurts dialogue more than it helps.
Partial pressure of atmospheric CO2 is not the limiting factor in growth for most plants. Increasing CO2 concentration will therefore not have a linear effect.
CO2 is a gaseous fertilizer, providing carbon to plants. But anyone that has ever kept a garden, or even a potted plant, knows that plants also need water, plus nitrogen, phosphorous, and potassium (N-P-K). Hydroponics growers can add to that list [Mg++], [Ca++], [SO4--], [Fe++], [Mn++], [Zn++], [Cu++], [BO3---], [MoO4--], and [Cl-] ions, usually present in the soil that is not used in a hydroponics system.
So increasing CO2 has diminishing returns, until further increase results in no further plant growth.
That global warming may induce more agriculture, and forest growth, in the global North is something I'd like to learn more about. Anyone have any further reading to recommend?