October 28th, 2009

woods, Elizabeth, camera, April

Climate Change I: sources of evidence for change

Although this is not a rant, it's also not an invitation for every anti-climate-change enthusiast in the known universe to come barging in here and argue.  You have your spaces to hold forth, which I don't go causing trouble in, and I have mine.

Having issued that warning, I was privy to another discussion in a closed list, and once more amazed at the misunderstanding of the original thesis and subsequent events within the scientific community as well as in the public mind.

The evidence for global warming did not come (never came) from climate models alone.  So rebuttals to global climate change based on the flaws of models misses the point.  The evidence comes from multiple sources.

1. The geological record of past climate and its relationship to various atmospheric conditions.  This research really began in the 1950s, when serious work with ice cores and pollen analysis, tree-ring data, and radiocarbon dating (less accurate but with a longer range) gave the first substantive links between physical and biological evidence of paleoclimates.  The International Geophysical Year (1957) gave a big push to such research, but some had begun before then.  In other words, through the 1950s, '60s, and '70s, and continuing to the present, increased data, increased refinement of research methods, and direct advancements in research methods, allowed scientists to correlate climate to atmospheric gas composition.

2. Geophysical evidence in the present day includes the rapid melting of glaciers and ice sheets and rising sea levels, rising global sea temperatures and global mean temperature, etc.; geochemical evidence includes higher carbon dioxide content of the air and increasing acidification of sea and fresh water.  

3. Meteorological evidence includes poleward shifting of dates of first frost, increased variability in seasonal temperatures and rainfall, increased variability in seasonal fluctuations of high-altitude winds (jet streams), etc.

4. Biological evidence includes the poleward migration of cold-intolerant plant species, poleward migration of cold-intolerant vertebrate and invertebrate species both in the oceans and on land, increasing desertification of semi-desert regions, winter survival of pest species formerly killed off by hard freezes.   In the Arctic, melting of permafrost has already begun on the flanks of melting glaciers, with release of additional greenhouse gases from the decay of long-frozen plant materials, only some of which carbon dioxide is used by the new plant cover.   A mismatch between migratory species and their food sources due to changes in temperature and rainfall that affect both plants and insects has been demonstrated in Europe and North America.

Contemporary changes are readily observable and have increased in the past 30 years.   Some of them I have personally observed: semi-tropical plants migrating two "planting zones" north, changes in migration patterns and the mismatch of food source to migrant,  milder winters in the past 10 years v. the previous 30, changes in rainfall patterns with a shift of jet streams to the north, etc.

To argue that these changes--predicted by the original hypothesis--are not caused by global warming would require an alternative explanation.  So far, no anti-climate-change enthusiast has offered such an explanation.

woods, Elizabeth, camera, April

Climate Change II : Effects of a Warming Change

The next issue is whether global warming is good or bad for a) the world as we know it and b) humans.  Aside from the enthusiasts for having apple orchards in the Arctic and banana trees in Brooklyn (yes, I actually read that some years back--someone thinking that you could easily turn tundra into farms) the harm done to our existing ecosystem and human society and culture is clear.

Global warming has a negative effect on agriculture--our food source--in multiple ways.   Successful agriculture depends on reliable frost-free dates, cooling hours (for crops that need cooling to produce fruit), length of growing season, and adequate fresh water.   So variability in dates of first and last frost,  number of cooling hours in winter, and rainfall intensity/frequency will have negative impacts on agriculture--including of course yields.   Hotter weather increases water use by crop plants and livestock, requiring more water for success.  At the same time, hotter weather increases evaporation from reservoirs that supply irrigation water and dries out the soil, reducing available soil moisture.  At the extremes, heat reduces crop health--the plant cannot take in enough water to sustain growth.  Extreme heat also affects how much fertilizer plants can utilize and how they react to pesticides.  They are more vulnerable to plant diseases and pest attacks.  As pest species move poleward, unhindered by winter freezes sufficient to knock back the population, crops are  subject to more and more attacks.  Poleward migration of species has already affected forestry (bark beetle infestations in southern Canada.)   Desertification also causes the loss of former productive land, as does sealevel rise (which can contaminate soils with salt even before they go underwater. 

Could we really use former permafrost in northern Canada and the newly uncovered barrens of Greenland to replace the agricultural land lost to desertification in the American Southwest, for instance?  No, for multiple reasons.  First, the warming climate is still unstable and thus relatively unpredictable.  Second, as permafrost melts it doesn't create immediately useful farm soils...and much of Greenland is rock scraped bare or into rock flour by its ice cap.   Some plants will grow there, but apple orchards and wheat fields are a long way away, if ever possible. 

Rising sea level will have a negative impact on all coastal populations:  that includes agriculture, urban development, and coastal industry. Coastal groundwater is already being invaded by salt water as the dual result of drawdown from its use and rising sea level, and coastal subsidence (from both human and other causes) is increasingly common. Pumping out of coastal aquifers and deep-pumping of petroleum have both been implicated.  Much of the world's population lives within 100 miles of a coast...and low, sloping coastal plains (the Gulf Coast of the U.S., much of coastal India and parts of coastal China, for example) will suffer significant losses with even modest sea-level rise.   Normal storm surges will cause increased coastal erosion, leading to more loss of land.   The Gulf Coast, for instance, is thick with major petrochemical plants producing fuel and other products for the rest of the country.    How hard would it be to move the infrastructure of the Gulf Coast inland 100 miles?   Here's one on a water front. 

Fresh water resources, even now barely sufficient for the human population, will be further limited by glacial melting: glaciers supply many of the highly populated river basins (including, in Europe, the Rhine.)  They will also be affected by sealevel rise, as the saltwater invades coastal and near-coastal aquifers.  And of course changes in rainfall distribution (not only in space but in time--and changing intensity/frequency) will affect freshwater availability.  

Poleward migration of insect populations has a direct effect on human health, as does lack of hard freeze to kill off populations and allow them to expand.  Tropical species, with the diseases they carry and the damage they can cause to human infrastructure, are a threat to human health.

Human populations thrive in temperate climates, not only because of the pervasiveness and severity of tropical diseases, but because like all mammals humans have a preferred temperature range in which their enzymes work optimally.   A few degrees Celsius of fever--loss of homeostatis for temperature--and humans die.   Even before that, their capacity to do useful work degrades.  Heat injury kills.  

So global warming has serious consequences for humans, as well as the existing ecosystems that have supported human populations throughout history.  It will cut the amount of arable land, cut crop yields, cut the supply of fresh water, and increase pressure from pests and diseases.

Whether the warming is caused by human activity or not, it's bad for us, as the  species we have become.  The earth has been warmer than it is likely to become...but there were no humans on it at the time.  We know humans can survive an Ice Age (they did) but we do not know if humans will survive a Hot Age.  It would be worth trying to slow or reverse global warming even if we were sure it was not anthropogenic.

But we aren't.

woods, Elizabeth, camera, April

Climate Change III : Why the Enemy Is Us

The arguments against a human cause of a) the increased carbon dioxide and b) global climate change rest on several false assumptions.   First, that because there are other sources of CO2, the human contribution must be so paltry as to be insignificant.   Second, that  CO2 isn't a major component of greenhousing--it's all sun cycles or something. 

But there again the evidence is on the side of the original thesis...that this round of global climate change is being accelerated by human activity.  In the paleoclimate record, high levels of carbon dioxide and methane are associated with warmer climates.  These are not the only "greenhouse gases" or the only contributors to the atmospheric change, but they are easy to measure.  Carbon dioxide was recognized as a greenhouse gas long before the climate-change hypothesis was raised--in fact, it was because it is a known greenhouse gas that rising carbon dioxide created an interest.

With increasing precision, it's possible to know how much geologic and other processes contribute to the levels of CO2 in the air.  It's possible to track entire air masses, with their associated chemical components (satellites are a big help.)  Samples of air at various altitudes allow comparison of the carbon isotope ratios in the carbon dioxide both vertically and across time.  So the human contribution to the atmosphere--across many atmospheric components, not just carbon dioxide--can be traced.   That contribution has increased rapidly in the past two centuries, both because of the increased population but also because of activities that decrease carbon uptake (reduction) via photosynthesis and increase carbon oxidation.

It does not matter that there are non-human-derived sources of CO2 and methane, such as volcanoes.   What matters, in terms of the anthropogenic component, is whether it's enough to tip the scales.   After all, if you're in a rowboat with a lot of water in it, just barely floating, and you reach over the side and dip another bucketful into the boat--you can indeed sink your own boat.  The last bucketful--the one that sinks the boat--may be a small fraction of what's in the boat, but it's a critical fraction.   If you're smart, you'll be dipping water from the boat and pouring it into the ocean. 

Humans have impacted this planet in many ways for tens of thousands of years, but that impact has accelerated as a) the population increased (it has about tripled in my lifetime) and b) developed more effective technology for changing the topography, vegetation, watercourses, etc. and using more resources per capita.  Population growth by itself would create changes in the surrounding ecosystems--could not help doing so. But combined with the technology that developed during and since the Industrial Revolution, humans have made visible, unmistakable changes to  the landforms, water supplies, and distribution of species.  Human activity has nearly always (and always in "civilizations") been aimed at short-term human benefit: this year's food supply, this year's water supply, this year's ease of transportation, etc.

That's natural--but the ways we go about it are not natural, and have demonstrable long-term  negative consequences, even not considering global climate.  A few thousand years ago, forest clearing in both Greece and China prompted a few to recognize that clear-cutting on slopes led to erosion, silty rivers (with more erosion downstream from the increased cutting power of  soil particles in the water), flooding, and so on.  Farming practices that were easy, but depleted soil fertility, have been common worldwide until farmers were forced to recognize the long-term futility of short-term exploitation.  Many such practices still exist, and have recurred in areas where the need to make a money profit (rather than feed one's own family or village) pushes farmers to try for maximum gain every year.

Urbanization and uncontrolled urban sprawl damaged ecosystems before anyone thought of global warming: industrial pollution of waterways was a subject of legal interest as early as 1250 in England, when butchers were constrained from throwing offal in the Thames (if they could be caught.)  Polluted water supplies--polluted by humans--still cause illness and disability, and degraded food supplies (fish too toxic to eat safely) around the world today.  The loss of productive farmland to development raised food prices (food had to be transported from farther away) in the 19th and 20th centuries, and still continues.  Damming of rivers interrupts migration of fish (and thus limits the fish species found above the dams and sometimes below) and in hot climates results in net loss of water through evaporation, while the stored water leaches salts (some even toxic) from the ground it sits on.

Air pollution of human origin has caused--and continues to cause--human disease and disability.  Asthma is the most obvious--but not the only--metric for the human cost of air pollution.  Agricultural, industrial, and home sources of air pollution markedly increase the risk of asthma and other conditions of the lung.  But air pollution does not limit itself to the lower levels of the atmosphere.  I remember flying to Chicago to a friend's wedding in 1970.  At that time, the air back home was still clear, seen from an aircraft.  But flying along the industrial northeast, we saw brown smog everywhere and came down through layers of yellow, orange, and brown--the mess extended to 20,000 feet. The chemicals that gave the colors created acidic conditions leading to acid rain (acid rain that fell hundreds or thousands of miles away, damaging the lakes and rivers and their fish...)  It was already known that cities created their own weather...that the air in the most rural areas, though purer than in cities, was not as pure as it had been.

Given that human activity was already having regional effects on the atmosphere, there's no reason to balk at the idea that human activity, if increased, could have global effects on the atmosphere, or that atmospheric and ground-level changes affect climate.  Beyond theory, those effects can now be demonstrated--as discussed in Climate Change I and II.   

Of course, no one has to accept the evidence.    You can play King Canute battling the tide if you want to.  Unfortunately, we don't have a way to offer each position in this a separate planet on which to play out their particular viewpoint and see who does best.   We have one planet, and one human race; all of us are in the boat together.    When there were only a few millions of us--even a couple of billion--we could play with putting more water in the boat and tossing water out--the boat was riding higher in the water.  Now--mistakes will be very costly indeed, costly not just in money, but in human lives.   You may think yours is safe...you may even dream of building a spaceship and going somewhere else...but right now, this is the boat we have.   Bailing it out seems better to me than sinking it.

woods, Elizabeth, camera, April

Climate Change IV: So What Options?

Leveling, if not reducing, CO2 and other greenhouse emissions should be a major goal.   The quickest and most massive way to lower them is to stop cutting down tropical forests.   CO2 emission is an immediate result of cutting down a rainforest tree: the soil is full of active decomposers who get to work on the tree's now-dead root system.  Decomposers, like us, use carbon-containing molecules as fuel--they use oxygen to burn the carbon and release CO2.   At the same time, the tree that was formerly fixing carbon is not doing it anymore.  Even before the carbon emissions that go with moving the tree to a sawmill, cutting it up, making things from it, shipping the wood, there's already that initial burst of CO2, and it's huge, at the rate tropical forests are going under.

Tree planting is important, but with the movement of pests into areas previously free of them (e.g. the pine bark and spruce bark beetle infestations in Canada) means that foresters and other arborists will have to consider carefully what they can plant that will fix the most carbon in the new conditions.  (Restoration ecologists have already considered how restoration ecology must change in the face of this changing climate.)   This will also require those who previously depended on wood for various uses to find other materials for those uses.

Taking steps to protect fresh-water resources is another essential step.  Here, the goal should be to ensure that rainfall isn't wasted, that aquifers aren't exhausted (which can lead to subsidence and to contamination of the remaining fresh water with nonpotable water, most commonly salt or sulfur-contaminated.)   In warmer climes, surface water storage of the current type will not be sustainable over the long haul (published data on evaporative loss forty years ago on some stations on the  Texas Mexico border exceeded 100 inches/year--in an area with average annual rainfall in the low 20 inches.)   Conversion of unsustainable agricultural lands in semi-desert areas to sustainable native vegetation should be considered;  get healthy short-grass going before things get worse, and it might be possible to retain some non-irrigated food production via low-intensity grazing.   Support of agricultural lands in ways that make them more sustainable (and thus often requiring less water for crops.) 

Switching from high-carbon energy sources to lower-carbon ones would also help. 

Population stability will be necessary some time in the future--we can't provide equitable living standards for the entire world population now, and should reduce population to the point where that is possible.   We waste human resources now to a scandalous degree--worse than wasting petroleum or coal--because we cannot provide the living standards necessary for everyone to achieve their potential.

These are only a few general suggestions--there are many more, and specifics for each individual in any situation (urban/rural/suburban/wealthy/poor, etc.) but though it would've been a heckuva lot easier to make changes 30-40 years ago...and 20 years ago...and even 10 years ago...we are where we are.