Category Archives: Peer Reviewed Article Review

“global renaissance of coal”

This article from the National Academy of Sciences says that although coal use is dropping in some developed countries and China, it is exploding in many developing countries.

Coal was central to the industrial revolution, but in the 20th century it increasingly was superseded by oil and gas. However, in recent years coal again has become the predominant source of global carbon emissions. We show that this trend of rapidly increasing coal-based emissions is not restricted to a few individual countries such as China. Rather, we are witnessing a global renaissance of coal majorly driven by poor, fast-growing countries that increasingly rely on coal to satisfy their growing energy demand. The low price of coal relative to gas and oil has played an important role in accelerating coal consumption since the end of the 1990s. In this article, we show that in the increasingly integrated global coal market the availability of a domestic coal resource does not have a statistically significant impact on the use of coal and related emissions. These findings have important implications for climate change mitigation: If future economic growth of poor countries is fueled mainly by coal, ambitious mitigation targets very likely will become infeasible. Building new coal power plant capacities will lead to lock-in effects for the next few decades. If that lock-in is to be avoided, international climate policy must find ways to offer viable alternatives to coal for developing countries.

 

nature and mental health

From the Proceedings of the National Academy of Science:

Urbanization has many benefits, but it also is associated with increased levels of mental illness, including depression. It has been suggested that decreased nature experience may help to explain the link between urbanization and mental illness. This suggestion is supported by a growing body of correlational and experimental evidence, which raises a further question: what mechanism(s) link decreased nature experience to the development of mental illness? One such mechanism might be the impact of nature exposure on rumination, a maladaptive pattern of self-referential thought that is associated with heightened risk for depression and other mental illnesses. We show in healthy participants that a brief nature experience, a 90-min walk in a natural setting, decreases both self-reported rumination and neural activity in the subgenual prefrontal cortex (sgPFC), whereas a 90-min walk in an urban setting has no such effects on self-reported rumination or neural activity. In other studies, the sgPFC has been associated with a self-focused behavioral withdrawal linked to rumination in both depressed and healthy individuals. This study reveals a pathway by which nature experience may improve mental well-being and suggests that accessible natural areas within urban contexts may be a critical resource for mental health in our rapidly urbanizing world.

vegetable rain gardens

Growing food in rain gardens – it seems almost too obvious. But it isn’t done much, and somebody has gone to the trouble of studying it scientifically here. They planted “beetroot, onion, spinach, tomato and broad bean”. This sounds good, but it might be fun to experiment with trees and other perennial species. There are some tough plants out there that will tolerate wet and dry conditions better than your typical annual garden crops. Jerusalem artichoke comes to mind, which is a sort of invasive American prairie flower that produces enormous amounts of delicious potato-like tubers.

gators and tigers and extinction, oh my!

The extinction rate is now 1000 times normal, says Duke University.

Not to worry, say Stanford, Berkeley, Princeton, and the University of Florida (and what would they know, those ‘gators with their beady dinosaur eyes), it’s only 114 times normal using “conservative assumptions”.

And according to a surprisingly edgy book review in my favorite special interest publication Civil Engineering (because what could be more special than my own interest), there is a new book out:

You probably don’t subscribe to Civil Engineering, so here is the Amazon description:

A growing number of scientists agree we are headed toward a mass extinction, perhaps in as little as 300 years. Already there have been five mass extinctions in the last 600 million years, including the Cretaceous Extinction, during which an asteroid knocked out the dinosaurs. Though these events were initially destructive, they were also prime movers of evolutionary change in nature. And we can see some of the warning signs of another extinction event coming, as our oceans lose both fish and oxygen. In The Next Species, Michael Tennesen questions what life might be like after it happens.

Tennesen discusses the future of nature and whether humans will make it through the bottleneck of extinction. Without man, could the seas regenerate to what they were before fishing vessels? Could life suddenly get very big as it did before the arrival of humans? And what if man survives the coming catastrophes, but in reduced populations? Would those groups be isolated enough to become distinct species? Could the conquest of Mars lead to another form of human? Could we upload our minds into a computer and live in a virtual reality? Or could genetic engineering create a more intelligent and long-lived creature that might shun the rest of us? And how would we recognize the next humans? Are they with us now?

climate change and the economy

Here’s another modeling study in Ecological Economics that looks at the effects of climate change on the global economy.

A demand-driven growth model involving capital accumulation and the dynamics of greenhouse gas (GHG) concentration is set up to examine macroeconomic issues raised by global warming, e.g. effects on output and employment of rising levels of GHG; offsets by mitigation; relationships among energy use and labor productivity, income distribution, and growth; the economic significance of the Jevons and other paradoxes; sustainable consumption and possible reductions in employment; and sources of instability and cyclicality implicit in the two-dimensional dynamical system. The emphasis is on the combination of biophysical limits and Post-Keynesian growth theory and the qualitative patterns of system adjustment and the dynamics that emerge.

DICE

This article in Ecological Economics reminded me of the DICE model from William Nordhaus at Yale.

In integrated assessment models (IAMs) economic activity leads to global warming, which causes future economic costs. However, typical IAMs do not explicitly represent the role of natural capital. In this paper, the DICE model by Nordhaus (2008) is expanded with a natural capital variable that is affected both by climate change and by depletive effects of economic activity. Due to a synergy between the two effects, the optimal policy of the expanded model features more and earlier abatement of CO2 emissions than DICE. Interestingly, the policy implications are different from what follows if one tries to capture the depletive effects on natural capital by simply reducing factor productivity growth in DICE. Acknowledging considerable uncertainty, simulations show that climate- and savings rate policies from the expanded model are more robust in the long term than policies that do not consider non-climatic depletion effects on natural capital.

The DICE model and a variety of papers related to it are freely available here.

meeting future food demand

This article in Water Resources Research says we have a shot at meeting future food demand.

Sustainable options for decreasing food demand and for increasing production include reduction of food losses on both the producer and consumer ends, elimination of unsustainable practices such as prolonged groundwater overdraft, closing of yield gaps with controlled expansions of nutrient application and irrigation, increases in crop yield and pest resistance through advances in biotechnology, and moderate expansion of rain fed cropland. Calculations based on reasonable assumptions suggest that such measures could meet the food needs of an increasing global population while protecting the environment.

social network theory and research

Here is a long paper with a lot of references on social network theory and empirical evidence, including learning and diffusion of innovations. For example,

A nice example of this using field data is a study of social learning by Conley and Udry (2001, 2004). They examine the use of fertilizer by pineapple farmers. In particular, they show that changes in the amount of fertilizer used by a given farmer are related to the success or failure of similar past changes in fertilizer use by other farmers. Having controlled experiments can substantially narrow down the range of explanations for observed peer correlations. For example, Hesselius, Johansson, and Nilsson (2009) examine absences in the workplace based on a randomized rule affecting about 3000 workplaces in G oteborg Sweden. Randomly
assigned agents were allowed to have longer spells of absence from work (14 days) without having to produce a doctor’s certificate than was the rule for the general population (8 days). This resulted not only in an increase in absences for the treated individuals (those allowed the extra time before producing a doctor’s certificate), but also for non-treated individuals conditional on being in a workplace with many treated individuals. Interestingly, the affect of how many other treated individuals there were in the workplace did not significantly influence treated individuals’ behavior. This allows them to distinguish between various ways in which the peer effects might work, ruling out things like enjoying time together and being more consistent with a fairness effect or related peer effect on preferences. This sort of study shows the power of (field) experiments in identifying peer effects…
The list of settings where peer effects, or network effects more generally, have been found to be important is a long and varied one. It includes a range of things from criminal behavior (Reiss (1980), Glaeser, Sacerdote and Scheinkman (1996), Kling, Ludwig and Katz (2005), Patacchini and Zenou (2008)), to education (e.g., Calvo-Armengol, Patacchini and Zenou (2008)), to risk-sharing and loan behavior (Fafchamps and Lund (2003), De Weerdt (2004), Karlan, Mobius, Rosenblatt, Szeidl (2009)), to obesity (Christakis and Fowler (2008), Fowler and Christakis (2008), and Halladay and Kwak (2009)). (See Fafchamps (This volume), Ioannides (This volume), Jackson and Yariv (This volume), Munshi (This volume), Sacerdote (This volume), and Topa (This volume), for more examples and background on empirical evidence.)

Paul Romer and “mathiness”

Paul Romer has attacked a number of fellow economists for relying on what he calls “mathiness” rather than mathematical theory. He believes the study of economic growth and its practical applications have suffered because of this.

Academic politics, like any other type of politics, is better served by words that are evocative and ambiguous, but if an argument is transparently political, economists interested in science will simply ignore it. The style that I am calling mathiness lets academic politics masquerade as science. Like mathematical theory, mathiness uses a mixture of words and symbols, but instead of making tight links, it leaves ample room for slippage between statements in natural versus formal language and between statements with theoretical as opposed to empirical content.

Solow’s (1956) mathematical theory of growth mapped the word “capital” onto a variable in his mathematical equations, and onto both data from national income accounts and objects like machines or structures that someone could observe directly. The tight connection between the word and the equations gave the word a precise meaning that facilitated equally tight connections between theoretical and empirical claims. Gary Becker’s (1962) mathematical theory of wages gave the words “human capital” the same precision and established the same two types of tight connection—between words and math and between theory and evidence. In this case as well, the relevant evidence ranged from aggregate data to formal microeconomic data to direct observation…

The market for mathematical theory can survive a few lemon articles filled with mathiness. Readers will put a small discount on any article with mathematical symbols, but will still find it worth their while to work through and verify that the formal arguments are correct, that the connection between the symbols and the words is tight, and that the theoretical concepts have implications for measurement and observation. But after readers have been disappointed too often by mathiness that wastes their time, they will stop taking seriously any paper that contains mathematical symbols. In response, authors will stop doing the hard work that it takes to supply real mathematical theory. If no one is putting in the work to distinguish between mathiness and mathematical theory, why not cut a few corners and take advantage of the slippage that mathiness allows? The market for mathematical theory will collapse. Only mathiness will be left. It will be worth little, but cheap to produce, so it might survive as entertainment.