Apr 7, 2014

Comparing the 2007 and 2014 IPCC WGII Summaries for Policymakers

This is a question of of tone and confidence. Which report provides a more stark view of the dangers of climate change? (I'm comparing the summaries since that's the only part the vast majority of people will read, and therefore is a good view on what the IPCC Working Group II wanted to emphasize.)

On current effects of climate change:

With regard to changes in snow, ice and frozen ground (including permafrost), there is high confidence that natural systems are affected...
Based on growing evidence, there is high confidence that the following effects on hydrological systems are occurring:

  • increased runoff and earlier spring peak discharge in many glacier- and snow-fed rivers [1.3]; 
  • warming of lakes and rivers in many regions, with effects on thermal structure and water quality

There is very high confidence, based on more evidence from a wider range of species, that recent warming is strongly affecting terrestrial biological systems...
Based on satellite observations since the early 1980s, there is high confidence that there has been a trend in many regions towards earlier ‘greening’ of vegetation in the spring linked to longer thermal growing seasons due to recent warming...
Much more evidence has accumulated over the past five years to indicate that changes in many physical and biological systems are linked to anthropogenic warming...
Effects of temperature increases have been documented in the following (medium confidence):

  • effects on agricultural and forestry management at Northern Hemisphere higher latitudes, such as earlier spring planting of crops, and alterations in disturbance regimes of forests due to fires and pests
  • some aspects of human health, such as heat-related mortality in Europe, infectious disease vectors in some areas, and allergenic pollen in Northern Hemisphere 
  • some human activities in the Arctic...and in lower-elevation alpine areas

Recent climate changes and climate variations are beginning to have effects on many other natural and human systems. However, based on the published literature, the impacts have not yet become established trends. Examples include:

  • Settlements in mountain regions are at enhanced risk of glacier lake outburst floods caused by melting glaciers...
  • In the Sahelian region of Africa, warmer and drier conditions have led to a reduced length of growing season with detrimental effects on crops. In southern Africa, longer dry seasons and more uncertain rainfall are prompting adaptation measures.
  • Sea-level rise and human development are together contributing to losses of coastal wetlands and mangroves and increasing damage from coastal flooding in many areas...

In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality (medium confidence)...
Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change (high confidence)...
Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have been more common than positive impacts (high confidence)...
At present the world-wide burden of human ill-health from climate change is relatively small compared with effects of other stressors and is not well quantified...
Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability (very high confidence)...
Climate-related hazards exacerbate other stressors, often with negative outcomes for livelihoods, especially for people living in poverty (high confidence)...
Violent conflict increases vulnerability to climate change (medium evidence, high agreement)...
The increase in confidence for farm yields and climate-related extremes alone makes the 2014 report significantly more blunt, in my view. Even the way the two are laid out is instructive: the 2007 report's findings are spread out over three pages, while 2014's are all grouped together under bolded headings. At the very minimum, they are at least equally stark.

On future effects of climate change:

These reports are fairly dissimilar, but let me choose the most similar samples I can find.


Five integrative reasons for concern (RFCs) provide a framework for summarizing key risks across sectors and regions. First identified in the IPCC Third Assessment Report, the RFCs illustrate the implications of warming and of adaptation limits for people, economies, and ecosystems. They provide one starting point for evaluating dangerous anthropogenic interference with the climate system. Risks for each RFC, updated based on assessment of the literature and expert judgments, are presented below and in Assessment Box SPM.1 Figure 1. All temperatures below are given as global average temperature change relative to 1986-2005 (“recent”).
(1) Unique and threatened systems: Some unique and threatened systems, including ecosystems and cultures, are already at risk from climate change (high confidence). The number of such systems at risk of severe consequences is higher with additional warming of around 1°C. Many species and systems with limited adaptive capacity are subject to very high risks with additional warming of 2°C, particularly Arctic-sea-ice and coral-reef systems. 
(2) Extreme weather events: Climate-change-related risks from extreme events, such as heat waves, extreme precipitation, and coastal flooding, are already moderate (high confidence) and high with 1°C additional warming (medium confidence). Risks associated with some types of extreme events (e.g., extreme heat) increase further at higher temperatures (high confidence). 
(3) Distribution of impacts: Risks are unevenly distributed and are generally greater for disadvantaged people and communities in countries at all levels of development. Risks are already moderate because of regionally differentiated climate-change impacts on crop production in particular (medium to high confidence). Based on projected decreases in regional crop yields and water availability, risks of unevenly distributed impacts are high for additional warming above 2°C (medium confidence). 
(4) Global aggregate impacts: Risks of global aggregate impacts are moderate for additional warming between 1-2°C, reflecting impacts to both Earth’s biodiversity and the overall global economy (medium confidence). Extensive biodiversity loss with associated loss of ecosystem goods and services results in high risks around 3°C additional warming (high confidence). Aggregate economic damages accelerate with increasing temperature (limited evidence, high agreement) but few quantitative estimates have been completed for additional warming around 3°C or above. 
(5) Large-scale singular events: With increasing warming, some physical systems or ecosystems may be at risk of abrupt and irreversible changes. Risks associated with such tipping points become moderate between 0-1°C additional warming, due to early warning signs that both warm-water coral reef and Arctic ecosystems are already experiencing irreversible regime shifts (medium confidence). Risks increase disproportionately as temperature increases between 1-2°C additional warming and become high above 3°C, due to the potential for a large and irreversible sea-level rise from ice sheet loss. For sustained warming greater than some threshold,44 near-complete loss of the Greenland ice sheet would occur over a millennium or more, contributing up to 7m of global mean sea-level rise.
Again, I think the 2014 report comes in with higher confidence, but really they aren't that much different. Overall, I judge these two are fairly close in terms of level of alarm. The big difference comes in terms of adaptation and mitigation, to which the 2014 report pays much more attention.

Mar 30, 2014

Dust storm

It's snowing again in DC apparently, but in the old hometown there's a hell of a dust storm going.

Update, about an hour later:

Mar 24, 2014

Matt Yglesias on Hippie-Punching Before and During the Iraq War

"Driving the ineffectual liberal response was the continuing near-pathological obsession with the far left, the sentiment that in a moment of national crisis the most important task facing liberalism was not to combat the errors of in-power conservatism but those of the hopelessly marginal left, who became the primary target of their rhetoric. In some cases, it seems reasonably clear that simple loathing of left-wing antiwar activists pushed liberal intellectuals into support of the Iraq War. But even many mainstream writers and pundits who would eventually reject the war contributed to the problem in the early postattack months, in effect firing in the wrong direction for so long that they wound up outnumbered and outgunned when they finally switched targets." -- Heads in the Sand

Mar 17, 2014

Good Grief

Three days to spring and this is the view off my back porch.

Mar 3, 2014

Feb 21, 2014

Piketty and Pop Culture

This piece was a little bit tongue-in-cheek:
The French economist Thomas Piketty has a new book coming out soon, Capital in the 21st Century. It is a great work, a fearsome beast of analysis stuffed with an awesome amount of empirical data, and will surely be a landmark study in economics. It also references The Aristocats, a 1970 animated Disney film about some upper-class cats who stand to inherit a fortune.
But there's actually kind of a genius technique there. Piketty uses pop culture references throughout the book (and not just Disney films, mind, but also Balzac and Austen) to show how the logic the economic system percolates down through a society. Austen's day was a time of extreme rentist inequality, so in her books the whole of upper-class life revolves around securing a big enough fortune to live "comfortably" on the interest (i.e., with 20-50 times the average income), because even profession work (like being a lawyer) didn't account for nearly so much money. It's a brilliant toehold not just for cultural analysis, but as a road into the general thesis.

Anyway, it's a great book. Well worth a look when it comes out.

Feb 18, 2014

How Wolves Changes Rivers

Turns out a keystone predator can have knock-on effects on a place that come all the way down to the actual geography of the waterways:

(h/t Bego)