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Sat Jun 20, 2020, 06:40 PM

Climate-driven risks to the climate mitigation potential of forests

The paper I'll discuss in this post is this one: Climate-driven risks to the climate mitigation potential of forests (William R. L. Anderegg,*, Anna T. Trugman, Grayson Badgley, Christa M. Anderson, Ann Bartuska, Philippe Ciais, Danny Cullenward, Christopher B. Field, Jeremy Freeman, Scott J. Goetz, Jeffrey A. Hicke0, Deborah Huntzinger, Robert B. Jackson, John Nickerson, Stephen Pacala, James T. Randerson, Science, 368, 1327 (2020))

One of the authors, Stephen Pacala, of Princeton University - where the esprit de corps centers around the belief that so called "renewable energy" will save the day, even though there is no evidence, beyond pure speculation that it will - was the co-author of the once (and possibly still) famous Socolow and Pacala "Wedgie Paper" of 2004, which talked all about how existing technologies, as of 2004, could be utilized to stop climate change dead in its tracks:

Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies (Socolow and Pacala, Science 13 Aug 2004:Vol. 305, Issue 5686, pp. 968-972)

One of the "Stabilization Wedges" (#5) was this one: 5. (Substitute) Gas baseload power for coal baseload power.

If you want to be amused, you can head on over to our beloved E&E forum here, or head over to Daily Kos, and read all about how "coal is dead." The rumor - let's call it what it is, "the big lie" - is that this result, the "death" of coal, is because of the zillion percent growth of so called renewable energy.

This year, as part of my subscription to Science they sent me an AAAS tee shirt with the suddenly controversial slogan on it "Facts are facts." This identity statement seems to have taken on a political context, which is why, when going to my physical therapy sessions where another patient wears her "Blue Lives Matter" tee shirt, I wear the shirt with the AAAS identity statement, which has become, um, political. On the left we think we embrace this identity statement and are thus somehow above and immune from embracing happy faced lies.

Of course, in the United States, our environmentalism is traditionally provincial. We think we can save the world by driving one of Elon Musk's cobalt laced cars.

But sorry, facts, are indeed facts. This is true for us on the left as well as it is for them on the right.

In this century, the use of coal grew by 63.22 exajoules to 159.98 exajoules up to and through 2018. This made coal the fastest growing source of energy in this century.

From 2017 to 2018, the increase in the use of coal amounted to 2.97 exajoules, compared to, in the same time frame, from 2017 to 2018, for solar, wind, geothermal and tidal energy combined an increase of 1.63 exajoules, slightly more than half the rate at which coal energy consumption grew.

2018 Edition of the World Energy Outlook Table 1.1 Page 38 (I have converted MTOE in the original table to the SI unit exajoules in this text.)

2019 Edition of the World Energy Outlook Table 1.1 Page 38] (I have converted MTOE in the original table to the SI unit exajoules in this text.)

In the week of August 13, 2004, when the famous "Wedgie" paper was published, (the week beginning August 8, 2004) the concentration of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere was 376.43. For the most recent week, pending tomorrow's result as of June 20, 2020, for the week beginning June 7, 2020, the concentration of the dangerous fossil fuel waste carbon dioxide was 416.34 ppm. This year, the running average annual increase over the last decade is 2.4 ppm/year, the highest figure ever recorded. In 2004, it was about 1.9 ppm/year.

Facts are facts. Facts matter.

Just because we in the United States are substituting gas for coal doesn't mean the world is. We like to have these silly big rock and roll concerts that are benefits for some thing or another, and all get together and sing "We Are The World," as if we were. But we are not the world. We are a province, more so than ever, under the dictatorship of the stupid. We are irrelevant, because the lives of poor people matter, and poor people fuel themselves with, um, coal, and biomass, and they (and we) die by the millions from air pollution while Princeton Professors mutter that "Nuclear Power is too dangerous." (Love you on talk Radio Michael Oppenheimer. You certainly don't remember me calling into a radio show on which you were a guest, where you talked about nuclear dangers. I'd guess it was about six or seven years ago, or about 40 or 50 million air pollution related deaths ago. I wonder how many people died from nuclear accidents in that time.)



To turn to the matter at hand: Even intellectual Lilliputians like the Orange Racist in the White House have climate solutions, and one of those he muttered, so I've heard, is the "Trillion Tree Initiative."

The minute I heard it, I muttered to myself, "Whence is the land and the water for this enterprise to come?"

Is it true that "trees are the answer?"

This review paper takes a look at the issue of how much forests can matter in addressing climate. (For perspective, the unit Pg (Petagram) is equal to 1 billion metric tons of carbon dioxide. Humanity adds, through combustion, about 35 to 36 billion metric tons of carbon dioxide to the atmosphere each year, and another 8 to 10 billion tons each year from land use changes.)

From the introduction:

Terrestrial ecosystems currently absorb ~30% of human carbon emissions each year (1), and forests account for the vast majority of this uptake [an estimated 8.8 Pg CO2e year−1 of a total land carbon uptake of 9.5 Pg CO2e year−1 over 2000–2007, where CO2e denotes CO2 equivalents (2, 3)]. A broad body of literature has focused for decades on the role of forests in the climate system (4–6), and forest-based natural climate solutions (F-NCSs) have experienced growing interest in recent years as a potentially major contributor to meeting Paris Agreement carbon targets (7–10). Forest-based strategies might provide up to 7 Pg CO2e of climate mitigation per year by 2030 at a carbon price of $100 per Mg CO2e, which is by far the largest potential category of natural climate solutions (NCSs) (7). Furthermore, many of these forest-based strategies are likely to have substantial cobenefits for biodiversity, ecosystem services, and conservation (9, 11).

Carbon policy that includes F-NCSs is building around the world (Fig. 1). For example, California has recognized 133 Tg CO2e in benefits from forest carbon offset projects in the United States between 2013 and 2019, with these credits making up a meaningful share of the compliance with the state’s cap-and-trade program (12). National and subnational government policies to reduce emissions have included forest projects, with policies in Japan, Australia, New Zealand, and British Columbia, Canada (Fig. 1). Additionally, many F-NCS projects have occurred under the framework of the United Nations’ Reducing Emissions from Deforestation and Degradation (REDD+) (13, 14) and under local and national emissions reduction goals...

I'm sorry, excuse me if I don't agree that California's 133 Tg (1 Teragram = 1 million tons) is meaningful. It's like announcing that spitting a lot will solve a drought.

The authors rapidly note that climatic changes might compromise this climate wedgie, in fact by doing something completely unusual in discussions of climate mitigation, looking at what is actually happening rather than what we predicted would happen. To wit:

Fundamental questions remain, however, about the fate of carbon stored in forests in a rapidly changing climate, particularly the extent to which climate change and climate-driven changes in disturbance regimes might compromise forest permanence (17–19). Climate-induced tree mortality events have been widely observed across the globe over the past few decades (20, 21). In addition to direct climate impacts on trees like drought events, additional disturbance agents including wildfire and insect outbreaks are sensitive to climate and have major carbon cycle consequences for forests (22–25). The biomass dynamics of an estimated 44% of forests globally are strongly sensitive to stand-replacing disturbance (including harvest) (Fig. 2) (26). Further, climate-driven tree mortality and disturbances are nonstationary (they change with time) and are projected to increase with climate change (25). Finally, due in part to the large uncertainties about climate impacts, CO2 fertilization, and disturbances in forests (27), Earth system model projections over the 21st century indicate that terrestrial ecosystems could sequester as much as 36.7 Pg CO2e year^(−1) or release as much as 22 Pg CO2e year^(−1) by 2100 for a high-emissions scenario (28).

Well, they do lapse into that famous word could at the end. That word has been thrown around my whole adult life about the environment. For example, I don't know how many times I've read about "studies" that "show" that "wind power could power the world by" (fill in a year that the current membership of Greenpeace will all be dead here).

If I heard one, I've heard many thousands, and I pretty much hear one at least once a week.

What could prevent forests from the terrestrial ecosystems that "could sequester as much as 36.7 Pg CO2e year^(−1)" from doing so?

The authors list possible threats to climate mitigation owing to, um, climate changes. Some Examples:


Fires in forests are perhaps the most well-quantified global disturbance and permanence risk. Between 1997 and 2016, an average of ~500 million ha of land burned each year, most of which is outside of forest ecosystems (36). Although burned area is declining in grasslands and savannas, burned area is increasing in many tropical, temperate, and boreal forest ecosystems (36). Fire in forests emits ~1.8 Pg CO2e year−1 (37, 38). Fire accounts for ~12% of stand-replacing disturbances in forest ecosystems annually (26) and is particularly important in key forest regions like the western United States, Australia, Mediterranean-type climates, and boreal forests in North America and Asia (39, 40). Climate-driven changes in fire regimes can affect permanence both through changes in burned area and through changes in fire behavior (i.e., fire temperature or scorch height) that influence tree mortality...



Globally, droughts represent a major and widespread permanence risk, underscored by the explosion of research relating to drought-induced tree mortality that has been done in the past decade (21, 52). Drought events have major impacts on forest carbon cycling through declines in productivity and carbon losses through mortality (20, 27). Major climate extremes explain up to 78% of the variation in global gross primary productivity in the past 30 years, and severe droughts made up ~60 to 90% of the largest extremes (53). As an example, the severe 2011–2015 drought in California killed more than an estimated 140 million trees and drove the full carbon balance of the state’s ecosystems to be a net source of −600 Tg CO2e from 2001 to 2015, which is equivalent to ~10% of the state’s greenhouse gas emissions over that period (54). A 2011 drought in Texas killed 9.5% of tree cover across the state...


...Biotic agents

Biotic disturbance agents, including insects and pathogens, cause substantial tree mortality globally. For example, bark beetles, which feed on tree phloem and introduce fungi that interrupt tree water transport, have killed billions of trees across millions of hectares of land in temperate and boreal coniferous forests in the past two decades (68–70) and have converted large regions of the Canadian boreal forest from a sink to a source over the course of a decade (34). Defoliators feed on leaves and can kill trees after multiple years of severe damage. Widespread tree mortality has occurred from defoliators in both coniferous and broad-leaved forests in temperate and boreal regions (24, 71). In addition to these native biotic agents, non-native invasive biotic disturbance agents are responsible for killing many trees globally. Prominent examples include Phytophthora-induced sudden oak death and the emerald ash borer in the United States and the red turpentine beetle in China (72)...


...Other disturbances

Other disturbances—particularly storms and wind-driven events, snow and ice events, and lightning—can also influence forest ecosystem carbon cycling (25, 83). These disturbance events can matter for local- to regional-scale carbon cycling in some areas but are thought to have relatively minor-to-modest global effects (25, 53). Hurricanes damage coastal forests and can have pronounced impacts on carbon budgets. For example, Hurricane Katrina damaged 320 million large trees that contained 385 Tg CO2e (83), and tropical cyclones had a net effect of a modest carbon source in the 20th century across U.S. forests (33)...

...and so on...

A few pictures from the text:

The caption:

Fig. 2 Sensitivity of global forest biomass dynamics to stand-replacing disturbance (excluding human land use changes) captured by disturbance return interval (years).

Warm colors indicate areas where biomass dynamics are highly sensitive to the frequency of stand-replacing disturbance and cool colors indicate areas that are relatively less sensitive. Redrawn from (26).

From the provinces, the only country that matters.

The caption:

Fig. 4 Climate change has already increased fire risk in ecosystems.

(A and B) Integrated 100-year fire risk of moderate- or high-severity fire from the Monitoring Trends in Burn Severity (MTBS) dataset based on fire occurrences in years 1984–2000 aggregated to ecoregions (A) and for fire occurrences in years 2001–2017 aggregated to ecoregions (B). Fire risk was computed as follows. First, within each ecoregion and year, a pixel-wise burn probability was computed as the fraction of pixels in that ecoregion labeled as moderate or severe fire, and these probabilities were then averaged in each time period. To project an integrated 100-year risk, we computed the probability of any pixel experiencing at least one fire under a binomial distribution with 100 trials and success probability given by the pixel-wise annual risk described above. This is a simple analysis that does not account for spatial or temporal autocorrelation or attempt to model any drivers of fire risk. Raw data obtained from www.mtbs.gov/direct-download, and Python code to create figures is available at https://github.com/carbonplan/forest-climate-risks.

Don't worry, be happy.

They'll be destroying our coastal shelf here in New Jersey with a big brand new array of steel towers - with steel being made from burning coal to heat coal to make coke - for wind turbines that in 20 years the people who are children and babies now will have to take down and dump at their expense, in a world with far fewer resources.

...that could be a generational justice issue...could it not?

There are people who call themselves "environmentalists" cheering loudly for this. I miss the days of John Muir, when "environmentalists" tried to prevent wilderness from becoming industrial parks.

That's what we think will save the world.

We couldn't be more clueless.

I wish all involved a happy fathers day tomorrow. I'm personally looking forward to it, even though deep down, I know I have no right to look young people in the eye.

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