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How Do We Know That Climate Change Will Be Mostly Bad?

Doc Snow writes about climate science and many other topics.

There is no more crucial question facing humanity today than climate change. Weather affects nearly everything, so changes to 'average' weather will affect nearly everything as well. Yet how, and even whether, we should respond has become subject to intensely polarized debate.

So what do the facts say, and how can we know which 'facts' to trust?

This article looks at why we should expect climate change to be, on balance, a bad thing.

How Do We Know Warming Will Be Mostly Bad?

Or, more formally:

How do we know that the observed or projected changes will be (on balance) bad?

Basic logic would suggest this, since Earth’s biosphere has adapted to conditions over hundreds of millennia. Startlingly, our food crops have almost all been developed over the past few thousand years, and are adapted to those relatively stable conditions. One would expect struggles to adapt to climatic changes happening in just decades. But “would expect” is not proof.

Truthfully, in many cases, we don’t have “proof.” Strictly, science does not deal in proof, but in disproof—the usual scientific model is to create a hypothesis, then do everything possible to show that that hypothesis is false. If it survives, then it is deemed to be true—until someone can think of a new test to disprove it, at least.

But this is not a very reasonable approach to managing risk. Suppose you have a balanced household budget, but you want a new car. What “proof” do you have that an additional expenditure of $250 a month will cause you to go broke—until, that is, you actually do?

We humans also tend to discount future risk. Consider the case of smoking. How many folks fail to be motivated to quit by the prospect of lung cancer ‘someday?’

'Sunny day flooding', Miami Beach.

'Sunny day flooding', Miami Beach.

Or consider Miami. It’s in great danger of inundation; 'business as usual' will create temperatures comparable to the Pliocene period of 3-5 million years ago. Accordingly, sea levels then were 10 to 40 meters higher. Such levels would submerge Miami, and indeed large chunks of Florida.

Yet no one appears excessively worried. "The deluge" is just too far off—despite the inconveniences of ‘sunny day flooding’ on Alton Road in Miami beach, now a semi-regular occurrence.

NOAA coastal flooding report cover.  Image courtesy NOAA; photo by Amy McGowan.

NOAA coastal flooding report cover. Image courtesy NOAA; photo by Amy McGowan.

Turns out, it's not just Miami Beach--though that city is ground zero for sea level rise problems in the US. A 2014 report from NOAA on what they termed 'nuisance flooding' shows such events to be increasing drastically. (Link in sidebar, photo above.)


A key finding:

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We stress that in many areas, the frequency of nuisance flooding is already on an accelerating trajectory, and many other locations will soon follow even with a continuation of linear SLRrel rates. This fact needs to be recognized, as it is critical for coastal planning entities to prevent critical-system degradation from SLR impacts and to promote resiliency efforts in general.

In other words, coastal flooding, whether at the level of a nuisance or, less commonly, a disaster, is going to become much more frequent, and we need to plan accordingly.

Changing flood frequencies, West Coast.  (Figure 7 from NOAA report.)  The story is similar for all coastal areas (Figs. 4-6).  Graphic courtesy NOAA.

Changing flood frequencies, West Coast. (Figure 7 from NOAA report.) The story is similar for all coastal areas (Figs. 4-6). Graphic courtesy NOAA.

More on Coastal Flooding in 2016-2017

South Florida, 5- and 10-meter sea level rise.  Image courtesy popsci.com, modified by author.

South Florida, 5- and 10-meter sea level rise. Image courtesy popsci.com, modified by author.

Benchmarking

Let’s consider some examples that afford us benchmarks.

Superstorm Sandy, for example, cost at least $68 billion in economic damage, and more than 200 lives. It was not ‘caused’ by climate change, and some of the reasons for its destructive power were apparently random—as for instance its New York landfall coinciding with an exceptionally strong high tide. Yet there is no doubt that lowering New York’s sea level by 8 inches—the amount of mean global sea level rise since 1880—would have reduced the storm’s flooding.

Flood surge expert Dr. Ben Strauss wrote that:

Sandy’s damage would absolutely still have been unthinkable without the extra 8 inches or so we might attribute to warming since the late 19th century. But you add about 6k people per vertical inch in this 8-9 ft elevation range. I think we all would have been happy to see just a few percent less damage here!

That means about 48,000 New Yorkers would have been spared flooding’s direct effects—a likely total of around 20,000 homes.

That doesn’t account for the likelihood that Sandy’s power was “juiced” by the warm sea surface temperatures the storm encountered as it grew.

It's Not the Humidity, It's the Heat

Or take heat waves, which are increasing.

The Russian heatwave of 2010 was a spectacularly terrible event; heat stress killed thousands, and there was drought, crop failure, and an enormous wildfire outbreak. Air pollution from those fires killed thousands more. Insurance giant Munich RE put combined mortality at 56,000, and economic damage at over $5 billion USD. (Some estimates approached $15 billion.)

Moscow street scene, before and during 2010 wildfires. Image courtesy Wikimedia Commons.

Moscow street scene, before and during 2010 wildfires. Image courtesy Wikimedia Commons.

What role did climate change play?

Rahmstorf and Comou (2011) found:

...an approximate 80% probability that the 2010 July heat record would not have occurred without climate warming.

That contrasts with earlier work by Dole et al., (2011) that found the event “mainly natural in origin.”

A follow up paper by Otto et al., (2012), concluded that there was:

...no substantive contradiction between these two papers, in that the same event can be both mostly internally-generated in terms of magnitude and mostly externally-driven in terms of occurrence-probability.

In essence, the papers were asking different questions: there were specific natural causes that led directly to the disaster, but also climate change made such conjunctions of circumstances far more likely.

The sign, translated, reads "To search for a Parisian victim of the heat wave, the City of Paris has implemented a hot-line: 0800 800 750."

The sign, translated, reads "To search for a Parisian victim of the heat wave, the City of Paris has implemented a hot-line: 0800 800 750."

More deadly still was the 2003 European heatwave, which afflicted a smaller but more densely populated area with some 70,000 total fatalities. Infrastructure damage and agricultural and other losses cost more than $10 billion USD.

One of the first-ever attribution studies found that the odds of such a summer had been at least doubled by anthropogenic climate change. A ten year anniversary study, Christidis et al., (2015), now reconsiders the odds:

...we find that events that would occur twice a century in the early 2000s are now expected to occur twice a decade. For the more extreme threshold observed in 2003, the return time reduces from thousands of years in the late twentieth century to about a hundred years in little over a decade.

Their Figure 3 shows that under the most severe emissions scenario, RCP 8.5, a typical summer of the 2020s will be considered startlingly cool by the 2090s.

Figure 3, Christidis et al (2014).  RCP 8.5 summers are described by the graph at the extreme upper right.

Figure 3, Christidis et al (2014). RCP 8.5 summers are described by the graph at the extreme upper right.

Extending The Benchmarks: What Do They Omit?

If we take just Sandy and the 2003 and 2010 heat waves, the total cost amounts to more than 130,000 premature deaths and economic loss of $85 billion USD or more.

One could expand the list of other possibly climate-related disasters considerably. To mention just a few:

  • Hurricane Katrina and Typhoon Haiyun/Yolanda;
  • Heatwaves in India and east Asia, 2010-present;
  • US drought, 2011-present.

As a very rough benchmark, it seems fair to conclude that climate change—due to just roughly 0.7-0.8 C of global warming—has probably cost humanity well in excess of 100,000 deaths and $100 billion USD in the current century.

But that still excludes much damage. Again, listing just a few examples:

  • Losses to natural ecosystems and to industries, such as fisheries, that depend upon them;
  • Hydrology-related losses, for example the currently-stressed California system, or the endangered glacier-fed water systems of cities like Lima;
  • Damage to indigenous people, such Canada’s Inuit, or Scandinavia’s Sami;
  • Risks of widespread biological extinctions;
  • Consequences of ocean acidification;
  • The combined acidification/warming threat to coral reefs worldwide—another serious episode of which was reported in late 2014.

It's important to note that impacts in all these areas are not speculative. They have already been reported—even though it remains very tough to quantify the degree of damage, or estimate just how bad damages will, or might, get.

Figure SPM.2a, from AR 5, WG 2:  a summary of global impacts.

Figure SPM.2a, from AR 5, WG 2: a summary of global impacts.

Tipping Points

Also excluded is the risk of so-called “tipping points”—that's Malcolm Gladwell's term, often broadly applied to possible ‘non-linearities’ in climate feedback processes.

"Non-linearities" doesn't convey much to most of us. So let's start with a physical image: this dinosaur figurine, posed on three legs.

This is the way it is meant to be seen:

how-do-we-know-that-climate-change-will-be-mostly-bad

But it's also reasonably stable ‘tipped’ onto the tripod formed by its raised leg and the two adjacent ones:

how-do-we-know-that-climate-change-will-be-mostly-bad

Those two positions could be energetically quite close to one another, with the slightest push of a finger serving to flip the dino from one position to the other.

Most stable of all, of course, would be this position:

how-do-we-know-that-climate-change-will-be-mostly-bad

The idea is that climate or earth systems, like the dinosaur, could have several possible states that are relatively stable, but which, given the right (or wrong) 'push', could rapidly transition into another state. Again, given adaptation to the existing state, that would imply biological and social challenges—and doubly so, given the rapidity of potential transitions.

Possible mechanisms that might ‘flip’ the planet into a warmer climatic state include:

  • Boreal forest dieback
  • Amazon rainforest dieback
  • Loss of Arctic and Antarctic sea ice (Polar ice packs) and melting of Greenland and Antarctic ice sheets
  • Disruption to Indian and West African monsoon
  • Formation of Atlantic deep water near the Arctic ocean, which is a component process of the thermohaline circulation.
  • Loss of permafrost, leading to potential Arctic methane release and clathrate gun effect

These mechanism have been identified based on evidence that they may have happened in the past. But there's little certainty.

Mark Lynas, author of "Six Degrees."

Mark Lynas, author of "Six Degrees."

Risk Again: Six Degrees

And that brings us back, once again, to risk. We know that many of the long-predicted impacts of human-driven climate change are now being observed. Some are, at this point, good—for example, in some areas crop yields have increased a bit with more warmth and longer growing seasons. In other cases, the impacts are not good at all—the increase in coral bleaching is an example. Our best assessment is that the more warming is allowed to continue, the more negative on balance the consequences will be.

A bleached colony of the soft coral known as "Bent Sea Rod," Florida, September 2014.  Photo by US Geological Survey, courtesy Wikimedia Commons.

A bleached colony of the soft coral known as "Bent Sea Rod," Florida, September 2014. Photo by US Geological Survey, courtesy Wikimedia Commons.

Right now, the warming observed is very modest. We are living in what author Mark Lynas terms the ‘One Degree World’—the world in which we are no more than one degree Celsius warmer than in pre-Industrial times. There is a consensus—more political than scientific in nature—that this ‘world’ is relatively benign, despite the odd heatwave or inundation disaster here and there, or the loss of a few marginal aboriginal cultures or obscure rainforest species.

The ‘Two Degree World’ is more challenging, but not (we think) unmanageably so. We would have a lot of trouble with our supplies of fresh water, and our supplies of seafood. We’d most likely be committing ourselves to a future without large chunks of many familiar coastal cities, from Miami to Mumbai. That means we’d also be committing ourselves to the relocation of probably hundreds of millions of people, and the loss of a great many species of wildlife. (Just how many of each is not easy to determine, but the numbers being debated are not comforting.)

But, the theory goes, we really don’t want to break into the ‘Three Degree World.’ In part, that is because the challenges to agriculture become yet greater, possibly resulting in “structural famine in the Tropics,” to use Lynas’s deceptively innocent-sounding phrase. But more significant is the possibility of reaching one or more ‘tipping points’.

Drought often means suffering for livestock, like this Brazilian goat, photographed in 2013 by Agência Brasil.  Image courtesy Wikimedia Commons.

Drought often means suffering for livestock, like this Brazilian goat, photographed in 2013 by Agência Brasil. Image courtesy Wikimedia Commons.

A cautionary study is Cox et al., (2000.) In its computer modeling runs, exceeding 2 C warming produced a dieback of the Amazonian forest. This in turn released enough carbon to put an additional 250 ppm CO2 into the atmosphere, and initiated an additional 1.5 C warming.

In other words, entry into the Three Degree World could commit us also to entry into the Five Degree World—and that world is, basically, hell. The environmental conditions we have relied on throughout our existence would be irretrievably gone. Every ecosystem on the planet would be reshuffled, with completely unpredictable (though certainly dire) results.

Work further investigating the Cox et al scenario so far remains inconclusive. We don’t know for sure that this is what would happen, but we can’t exclude it. It could very well happen.

Satellite view of deforestation in Rondônia, western Brazil, 2012, by NASA, modified by author.  Original page shows progression from 2000.

Satellite view of deforestation in Rondônia, western Brazil, 2012, by NASA, modified by author. Original page shows progression from 2000.

So, the impacts remain, as scientists say, ‘poorly constrained.’

  • We know many things that are happening now, but we don’t know how bad they could ultimately be.
  • We know that there is some ‘upside’ to warming, but we are pretty sure that it gets smaller and smaller (relative to the 'downside') the more warming we allow.
  • We know that we could lose what control over the process we now have, but we don't know when.

The risks, policies, and ideas involved are all ‘big’, compared to our individual concerns, and often seem remote, in space, in time, or both. And so we tend not to worry as much as we should.

But, in Terri Garthwaite’s phrase, this world “is our children’s house.” Knowing just some of the risks, do we really want to live without any ‘climate insurance?’

how-do-we-know-that-climate-change-will-be-mostly-bad

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