Impacts of Modest Global Warming

What will happen if our planet’s atmosphere warms 2 degrees Celsius during this century? I don’t know. I haven’t seen studies of warming to that extent (and I would welcome any links to studies that exist.)


What we’ve seen is mostly media reports of what will happen if temperatures rise much higher and most of those reports are pretty over-dramatic. But a careful study of modest temperature rises would be useful–after all, even if temperatures do climb higher, they will pass through the 2C range and perhaps stay there for quite a while.

The impacts that I have seen discussed are mostly on an unspecified gradient, which may be the best climate science can do at present. At some point between temperature rises of 1C and 4C, disruptions of large scale weather phenomena, such as the monsoon cycle, are expected to occur. But we don’t know at what point.

Similarly, although CO2 helps plants to grow and to use less water, there is a drop off effect–after a certain point CO2 doesn’t help as much. At what level of warming will we see the break point for CO2?

We really haven’t seen the projected climate refugees or climate deaths so far this century, but I would tend to assume that the hiatus in global warming is at least one plausible explanation for our good fortune. But I haven’t seen a linking between specific levels of warming and deaths or conflicts. Is any warming certain to cause people to flee their homes due to drought, storm or flood? Is any warming enough to cause the next Syrian refugee crisis? Or are there threshold levels? If so, what are they?

Are impacts expected to be linear? Are there step changes? I’ve read all the IPCC reports and still don’t have an answer to any of these questions. Perhaps I read too casually. If so, again, please point out to me where I should continue my investigation.

This stuff matters.

16 responses to “Impacts of Modest Global Warming

  1. On the “100 years” branch, I note that “Greenland melts” is associated with a 2°C rise. That’s an exaggeration beyond satire.

  2. Tom writes:”…although CO2 helps plants to grow and to use less water, there is a drop off effect–after a certain point CO2 doesn’t help as much. At what level of warming will we see the break point for CO2?

    This is not in accord with what we know. Climate change is already net negative. “Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have been more common than positive impacts (high confidence).” – IPCC WGII AR5,

    There is *already* a net negative impact.

    • No, climate change is not net negative. Food crops,up Storms, flat. droughts, flat. No climate refugees. No islands disappearing from slr. Bangladesh just fine.
      And besides, troll, the climate is always changing. So you are a fool and a troll for even relying on the cheap idiocratic new coke name for global warming.

    • Kevin, in the warmest year in period of recorded temperatures, our planet set world records for agricultural output. The FAO notes a greening of the Sahel and even the Gobi.

      Is there something you just don’t like about reality?

  3. hunter – the quote from Tom is about CO2 affects on plants. The IPCC has stated with high confidence that the effects are already net negative. This has nothing to do with refugees, storms per se, or islands disappearing.

    Please learn to read and comprehend.

    Have you figured out, yet, that adjustments to the global land/sea temperatures *reduce* the warming trend?

    • Kevin,
      The IPCC also stated with authority that Tibet glaciers were disappearing in a few more years. Paid circle jerks of hype like the IPCC are good for jerks to admire.
      And yes, you are tediously echoing your delusions about adjustments moderating things and demonstrating your math illiteracy. I get it: You are ignorant. No problem, nothing new or unexpected.
      Troll on.
      And your ignorance about plant metabolism is notable as well.
      “When and how much CO2 ?

      Generally, enriching the garden’s air to raise the level between 1,000 and 1,500 ppm is recommended. There is apparently no benefit to augment the concentration higher than 1,500 ppm. Higher levels are a human health hazard. Plants do not benefit from higher levels either. That can also be a waste of money. But for exceptional species, most plants breathe CO2 only during photosynthesis which is when there is light.”
      And here is a table of upper limits on CO2 tolerance in crop plants:

      The digits to the immediate left of the plant species are *percentages * of CO2.
      In other words, my math illiterate friend, CO2 will have to increase from ~400ppm to ~10,000ppm to even impact something as CO2 sensitive as an onion.

      Kader (1997b), and Saltveit (1997)).
      CO2 (%) Commodity
      1 Onion (long term) (Allium cepa L.)
      2 Lettuce (crisphead) (Lactuca sativa L.)
      Pear (Pyrus communis L.)
      3 Artichoke (Cynara scolymus L.)
      Tomato [Lycopersicon esculentum (L.) Mill.]
      5 Apple (most cultivars) (Malus ´domestica Borkh.]
      Apricot (Prunus armeniaca L.)
      Carrot (Daucus carota L.)
      Cauliflower (Brassica oleracea L. Group Botrytis)
      Cucumber (Cucumis sativus L.)
      Grape (Vitis vinifera L.)
      Nashi (Pyrus serotina Rehd.)
      Olive (Olea europaea L.)
      Orange [Citrus sinensis (L.) Osb.]
      Peach (clingstone) [Prunus persica (L.) Batsch]
      Potato (Solanum tuberosum L.)
      Pepper (bell) (Capsicum annuum L.)
      7 Banana (Musa sp.)
      Bean (green snap) (Phaseolus vulgaris L.)
      Kiwifruit [Actinidia deliciosa (A. Chev) C.F. Liang et A.R. Ferguson var. deliciosa]
      8 Papaya (Carica papaya L.)
      10 Asparagus (Asparagus officinalis L.)
      Brussels sprouts (Brassica oleracea L. Group Gemmifera)
      Cabbage (Brassica oleracea L. Group Capitata)
      Celery [Apium graveolens L. dulce (Mill.) Pers.]
      Grapefruit (Citrus paradisi Macf.)
      Lemon (Citrus jambhiri Lush.)
      Lime (Citrus limettioides Tan)
      Mango (Manifera indica L.)
      Nectarine [Prunus persica (L.) Batsch Group Nectarine]
      Onion (short term) (Allium cepa L.)
      Peach (freestone)
      Persimmon (Diospyros kaki L.)
      Pineapple [Ananas comosus (L.) Merr.]
      Sweetcorn (Zea mays L.)
      15 Avocado (Persea americana Mill.)
      Broccoli (Brassica oleracea L. Group Italica)
      Lychee (Litchi chinensis Sonn.)
      Plum (Prunus ´domestica L.)
      Pomegranate (Punica granatum L.)
      Spinach (Spinacia oleracea L.)
      Sweetsop (Annona squamosa L.)
      20 Cantaloupe (muskmelon) (Cucumis melo L.)
      Durian (Durio zibethinus Murr.)
      Mushroom (Agaricus bisporus L.)
      Rambutan (Nephelium lappaceum L.)
      25 Blackberry (Rubus L. subg. Rubus Watson)
      Blueberry (Vaccinium corymbosum L.)
      Fig (Ficus carica L.)
      Raspberry (Rubus idaeus L.)
      Strawberry (Fragaria ´ananassa Duch.)
      Climate kooks are just the latest jugheads who get off on thinking about the Apocalypse.

      • Kevin ONeill

        hunter – I don’t know of anyone that claims that the level of CO2 is a direct negative impact on plants. In fact, that’s the part that’s a benefit. The negative impact is due to increased temperature. You’ve built a strawman and have soundly defeated it. Hooray 🙂

        ‘Net’ in these discussions implies there are both positive and negative effects. Once again, your failure to read and comprehend has revealed you as not exactly the sharpest knife in the drawer. It’s time to buy a clue.

        What you should have been looking at was not the direct effect of CO2 on plant growth, but processes like evapotranspiration. Here’s just one little excerpt:
        Carnegie scientists Long Cao and Ken Caldeira doubled the level of carbon dioxide in their model and found that globally the reduced evapotranspiration was responsible for 16 percent of the land warming; the rest was due to CO2’s heat-trapping effects. In North America and Asia, more than 25 percent of the warming was due to the impact of increased CO2 on vegetation. “There is no longer any doubt that carbon dioxide decreases evaporative cooling by plants and that this decreased cooling adds to global warming,” said Cao. “This effect would cause significant warming even if carbon dioxide were not a greenhouse gas.”

        Thank you for playing, hunter. But do please try to read *and* comprehend next time.

      • Kevin ONeill

        hunter, and I shouldn’t have to remind you that you’re also going to have to figure in heat stress, the effects of increased drought, increased flooding, and increased wildfires.

        There are benefits, if we move to Siberia or Canada some of that frozen tundra (not Lambeau Field) might be suitable for farming. Unfortunately it’s not exactly the greatest topsoil around.

        You see my friend, brighter minds than yours (or mine) have already weighed the pros and cons – and on net they see it as a negative. You of course with your full-on D-K are much smarter than them – even though you do have a slight problem reading and comprehending. But hey – denying what science tells us is pretty much your middle name now, isn’t it?

      • Those brighter minds that have published papers reviewed by the IPCC have agreed that impacts on agriculture are for the future, not the present. Starting about 2040, if warming continues.

        Their intelligence in this matter is supported by reality–agricultural output increases, as does vegetation cover on the planet overall, showing to all but the most stubborn that any impacts human caused climate change have on agriculture are future, not present.

      • Kevin,
        Find an agriculturally significant plant whose various variteites cannot handle a ~1-2o increase in temp. and still maintain produtivity.
        Let me know if you find anything.
        You are just arm waving- you said CO2 was going to cause a problem in productivity, I demonstrated you are wrong and now you are being a little whiner and hoping to change the subject to heat stress.
        Hint: Corn, rice and other grain crops came out of the tropics and were bred to thrive in colder climates. Typical climate kook that you are, you ignore the facts when they prove you wrong, move the gola posts and pretend you are right, no matter the lack of support for your hysterical position.

  4. I note that according to their chart, there are already extinct species. Trouble is, when challenged to name a species, there is a lot of arm waving and waffling. Surely if there is a plant or animal no longer out there, it should be a poster child for the movement.
    I love their more earthquakes – no doubt there is peer reviewed literature on that on as well.

    If they can’t even get the past correct, what faith can one have in the rest of their chart?

  5. ChrisM —
    I seemed to recall a recent paper suggesting that climate change would cause more earthquakes, so I started to search for it. But I got distracted by a column published in 2011:

    [S]cientists have for the first time released a study that indicates that man made changes to our climate are also quite probably effecting the movement of tectonic plates around the globe as well. The implications of their research are far ranging as well as frightening.

    There was another hit from the same time, from Agence France-Presse discussing the same paper. The Agence France-Presse discussion was more measured, and included this:

    Iaffaldano [the paper’s lead author] stressed that his study did not mean that global warming would translate to stronger earthquakes happening more often, with the relevant patterns developing over “the order of millions of years.”

    “Of course earthquakes do occur at the boundaries between plates because of plate motions, but our work doesn’t imply at all that we will see an increase in these types of events,” he told AFP.

    It didn’t stop the author of the first column from trying to magnify this into a crisis, though. Some people seem determined to *not* consider things in proportion. I recall reading a breathless comment a few years ago which took alarm at a [then-]recent estimate from GRACE that Greenland was losing 100 BILLION TONS of ice per year. Sea level rise is really dangerous! Now 100 Gtons/year of ice melt results in only 1 inch per century of sea level rise, but that’s no reason not to panic, is it?

  6. Tom, there is a bigger problem with the impact calculation that you might want to explore. Fundamentally in the models, you have a few things,
    more CO2-> more warming.
    more economic growth -> more CO2
    more warming -> more damages

    However, more economic growth also means less damages as countries are better able to adapt.
    They have built a damage prognosis for the current world, but the world that is impacted will be one that is wealthier. The more warming they predict, the wealthier the world.

    • MikeN,
      The problem with the current climate models and damage models is that they are so bad they are not even wrong.

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