A Promise: Computer models
Scott K Johnson has written an article at ArsTechnica on computer models. It's a behind-the-scenes look and I like the way it's written for a broader audience. A tiny taste with two excerpts (my bold italics):
Climate models are, at heart, giant bundles of equations—mathematical representations of everything we’ve learned about the climate system. Equations for the physics of absorbing energy from the Sun’s radiation. Equations for atmospheric and oceanic circulation. Equations for chemical cycles. Equations for the growth of vegetation. Some of these equations are simple physical laws, but some are empirical approximations of processes that occur at a scale too small to be simulated directly....
...Steve Easterbrook, a professor of computer science at the University of Toronto, has been studying climate models for several years. “I'd done a lot of research in the past studying the development of commercial and open source software systems, including four years with NASA studying the verification and validation processes used on their spacecraft flight control software,” he told Ars.
When Easterbrook started looking into the processes followed by climate modeling groups, he was surprised by what he found. “I expected to see a messy process, dominated by quick fixes and muddling through, as that's the typical practice in much small-scale scientific software. What I found instead was a community that takes very seriously the importance of rigorous testing, and which is already using most of the tools a modern software development company would use (version control, automated testing, bug tracking systems, a planned release cycle, etc.).”
Read the full article at ArsTechnica here.
If you get the taste for exploring computer models, go to Isaac Held's blog. There was also an interesting technical discussion at William Connolley's place, Stoat, a few weeks ago.
A Threat: Climate change leads to conflict - a striking convergence of results
Seems logical, but is there any evidence? There's a new paper in Science (paywalled) that explores the evidence through an analysis of 60 quantitative studies. You can download the paper here. Here is the abstract:
A rapidly growing body of research examines whether human conflict can be affected by climatic changes. Drawing from archaeology, criminology, economics, geography, history, political science, and psychology, we assemble and analyze the 60 most rigorous quantitative studies and document, for the first time, a striking convergence of results. We find strong causal evidence linking climatic events to human conflict across a range of spatial and temporal scales and across all major regions of the world.
The magnitude of climate’s influence is substantial: for each one standard deviation (1σ) change in climate toward warmer temperatures or more extreme rainfall, median estimates indicate that the frequency of interpersonal violence rises 4% and the frequency of intergroup conflict rises 14%. Because locations throughout the inhabited world are expected to warm 2σ to 4σ by 2050, amplified rates of human conflict could represent a large and critical impact of anthropogenic climate change.The last paragraph suggests that we learn more about the underlying causes so as to minimise conflict as global warming kicks in. Will we? In fifty years' time there will still be deniers expecting an ice age "any day now", arguing that "the world hasn't warmed since 2062". At some stage the rest of us will decide to ignore them completely.
Numerous competing theories have been proposed to explain the linkages between the climate and human conflict, but none have been convincingly rejected, and all appear to be consistent with at least some existing results. It seems likely that climatic changes influence conflict through multiple pathways that may differ between contexts, and innovative research to identify these mechanisms is a top research priority. Achieving this research objective holds great promise, as the policies and institutions necessary for conflict resolution can be built only if we understand why conflicts arise. The success of such institutions will be increasingly important in the coming decades, as changes in climatic conditions amplify the risk of human conflicts.Hsiang, Solomon M., Marshall Burke, and Edward Miguel. "Quantifying the influence of climate on human conflict." Science (2013): DOI: 10.1126/science.1235367.
A Promise: Advances in solar technology - making it cheaper and more efficient
And in Nature this week, there's a paper describing a new solar technology (paywalled). According to Science News, this could lead to much cheaper solar cells "possibly for as little as $0.15 per watt, or one-quarter the price of thin-film silicon devices".
The work was described in Science News (excerpts):
A solar cell converts sunlight into electricity. A typical cell contains layers of materials known as semiconductors—most often silicon. When a particle of light, or photon, strikes an atom in one of these semiconductors, it knocks free a negative electron that can scoot through the material and leaves behind a positively charged "hole" that can also move about. The electrons and holes travel in opposite directions, through layers of semiconductors with different properties, to create a flow of current...So far, improving the efficiency of solar technology has used very expensive semiconductors such as gallium arsenide. Recently scientists have been experimenting with perovskites, which can be tuned to absorb sunlight. Perovskites are "compounds such as calcium titanium oxide in which the atoms arrange themselves in a particular mix of cube and diamond shapes". There have been some twists and turns - with promising results (my bold):
...Last year saw a breakthrough for perovskite cells, however, when physicist Henry Snaith at the University of Oxford in the United Kingdom and colleagues discovered that the devices actually worked better if they replaced the semiconducting bubbles with an insulating scaffold. The perovskite, as it turned out, was a pretty good semiconductor, and could shift electrons efficiently by itself.
Now, Snaith and colleagues have delivered another surprise: The bubblelike nanostructure is completely irrelevant. The Oxford team has demonstrated that perovskite cells are just as efficient if they are constructed in the same flat design, and using the same method—known as vapor deposition—as cheap thin-film silicon cells. “Having started with a complicated nanostructure, we’ve reduced it to a thin film,” Snaith says. “It’s amusing, I agree!”
What's more, the simple layered cell converts more than 15% of sunlight to electricity—equal to the record for perovskite cells, set just 2 months ago for a nanostructured device—as the researchers report today in Nature. Had physicists known perovskite was a good semiconductor, they probably would have started off with a regular, thin-film cell, Snaith says.
Perovskite cells now have a greater chance of hitting the mainstream market—possibly for as little as $0.15 per watt, or one-quarter the price of thin-film silicon devices, Snaith says.
Mingzhen Liu, Michael B. Johnston & Henry J. Snaith, Efficient planar heterojunction perovskite solar cells by vapour deposition, Nature (2013) DOI: 10.1038/nature12509
