Hierarchy: Part II:1:A:v.
Back to Intro - Back to Outline - Back to Bullet vi
Introduction
Most plants and animals rely on climate to provide the necessary conditions to provide essential sustenance. Additionally, living organisms rely on climate to provide weather cues essential to a complete life-cycle. Therefore, widespread warming should have a measurable effect on the life-cycles of many plants and animals. With increased temperatures, birds migrate and lay eggs sooner, populations tend poleward, and the physical and genetic traits of many species tend toward configurations ideal for warmer climates. Almost certainly a majority of these effects are not known, but those that are known are easy to measure and stand as a completely independent and reliable complement to temperature data. Accumulating data from these sources avoids many of the issues endemic to outright temperature measurements, such as instrumentation unreliability, faulty or problematic calibration, and lack of continuity or comprehensiveness of records. However species' traits are poor measurers of the degree of the warming, meaning that their use is restricted to orthogonal verification of more standard climatic data.
Study 1:
Fingerprints of global warming on wild animals and plants
Terry L. Root et. al., Nature 421, 37-42 (2 January 2003)
Basic: A large meta-analysis of 143 independent papers which shows that the large majority [>80%] of nearly 1,500 plant and animal species studied had significant changes in behavior, habits, and physical traits consistent with rising temperatures but not consistent with level or decreasing temperatures. The trait shifts were statistically significant in the direction consistent with warming.
Details: The species' traits studied included population density change and poleward migration; phenology: the timing of egg-laying, flowering, migration, etc.; morphology: body size, behavior, etc.; and genetic frequency shifts. The meta-study identified potential temperature-dependent shifts for each species and counted the number of observed shifts of these types. Over 80% of the species showed shifts consistent with warming, with a 90% confidence interval of roughly 70%-89%. The shifts in phenology [timing of life-cycle events] across species shows statistically significant trends towards earlier dates.
In sum: "...the balance of evidence suggests that a significant impact of recent climatic warming is discernible in the form of long-term, large-scale alterations of animal and plant polulations. For example, the average shift in spring phenology (timing) of events, such as breeding or blooming, for temperate-zone species is 5.1 +/- 0.1 days earlier in a decade."
Discussion: It is important to note that this study does two important things: [1] confirm a wide-spread and broad-based response consistent with a global warming trend, and [2] act as an independent, statistically verified, though imprecise, verification of the IPCC warming data. Though the IPCC data were cited in the study, it is crucial to understand that the trait shift data exist independent of any warming data and no statistical results were contingent on IPCC data.
Terry L. Root et. al., Nature 421, 37-42 (2 January 2003)
Basic: A large meta-analysis of 143 independent papers which shows that the large majority [>80%] of nearly 1,500 plant and animal species studied had significant changes in behavior, habits, and physical traits consistent with rising temperatures but not consistent with level or decreasing temperatures. The trait shifts were statistically significant in the direction consistent with warming.
Details: The species' traits studied included population density change and poleward migration; phenology: the timing of egg-laying, flowering, migration, etc.; morphology: body size, behavior, etc.; and genetic frequency shifts. The meta-study identified potential temperature-dependent shifts for each species and counted the number of observed shifts of these types. Over 80% of the species showed shifts consistent with warming, with a 90% confidence interval of roughly 70%-89%. The shifts in phenology [timing of life-cycle events] across species shows statistically significant trends towards earlier dates.
In sum: "...the balance of evidence suggests that a significant impact of recent climatic warming is discernible in the form of long-term, large-scale alterations of animal and plant polulations. For example, the average shift in spring phenology (timing) of events, such as breeding or blooming, for temperate-zone species is 5.1 +/- 0.1 days earlier in a decade."
Discussion: It is important to note that this study does two important things: [1] confirm a wide-spread and broad-based response consistent with a global warming trend, and [2] act as an independent, statistically verified, though imprecise, verification of the IPCC warming data. Though the IPCC data were cited in the study, it is crucial to understand that the trait shift data exist independent of any warming data and no statistical results were contingent on IPCC data.
Conclusion: This meta-analysis is very strong evidence of a widespread warming trend.
Study 2:
Biological fingerprint of climate change impacts
Camille Parmesan & Gary Yohe, Nature 421, 57-60 (2 January 2003)
Basic: A large meta-analysis of over 1,700 species focusing on range and phenology shifts as well as relative abundance shifts. The shifts are compared to predictions based on IPCC climate warming data and agree with a confidence of >95%. This means that there is a less than 5% chance that the living systems' shifts that have been observed are correlated with the IPCC warming data purely by chance.
Details: Northern range limits for species moved an average of 6.1 km per decade northward with 95% confidence interval of 1.3-10.9. Mean spring timing advanced an average of 2.3 days per decade, with 95% confidence interval of 1.7-3.2. The entire set of analyses points to a >95% [the IPCC's definition of "very high"] confidence that climate change is driving species poleward and pulling spring dates earlier.
In sum: "The meta-analyses of 334 species and the global analyses of 1,570 species... show highly significant, nonrandom patterns of change in accord with observed climate warming in the twentieth century, indicating a very high confidence (>95%) in a global climate change fingerprint."
Discussion: This is perhaps the most statistically rigorous paper on the topic. Conforming to very high levels of objectivity and statistics, the evidence overwhelmingly proves that global plant and animal life is changing in ways consistent only with global warming. We endeavor in this section only to show that plants and animals are changing in ways that signal global warming, but it is interesting to note that this paper also ties the degree of living organism response to the amount of warming and thus acts as a kind of verification of the actual IPCC warming data.
Conclusion: This meta-analysis is very strong evidence of a global warming trend.
Study 3:
[Various phenology studies]
Mark D. Schwartz
[as suggested by reader "Smoker"]
Basic: Schwartz has made a career out of creating an integrated study of phenology. He utilizes ground stations, citizen scientists, networks of researchers and satellites to track the onset of spring and to measure trends in the timing of leafing and blooming. There is no simple way to synthesize all of his findings here, but there is a very useful collection of figures on his website relating to a single study he conducted which is indicative of the type of data he is collecting. The figures for growing season length, last spring freeze date, first bloom date, and first leaf date trends are particularly instructive. Data from stations across the Northern Hemisphere were used for the study.
One pertinent quote: "Results are consistent with prior smaller area studies, confirming a nearly universal quicker onset of early spring warmth (spring indices (SI) first leaf date, -1.2 days per decade), late spring warmth (SI first bloom date, -1.0 days per decade; last spring day below 5 1C, -1.4 days per decade), and last spring freeze date (-1.5 days per decade) across most temperate NH land regions over the 1955–2002 period."
[Quoted from: Onset of spring starting earlier across the Northern Hemisphere, Mark D Schwartz et. al., Global Change Biology (2006) 12, 343]
Conclusion: This body of data is very strong evidence of a widespread warming trend.
Further studies on the topic:
Patterns of phenological changes in migratory birds
Thorup K et. al., Oecologia. 2007 Apr;151(4)
Rapid advance of spring arrival dates in long-distance migratory birds [with response]
Jonzen N, et. al., Science. 2006 Jun 30;312(5782)
Climate correlates of 20 years of trophic changes in a high-elevation riparian system
Martin TE, Ecology. 2007 Feb;88(2):367-80
Conclusion
These studies together constitute conclusive evidence of a global warming trend. Little information about the rate and scale of the warming is discernible from this data, however. No papers I have found to date can attribute these trait shifts to any other cause than increasing temperatures, so this bullet is uncharacteristically clean and simple.
Bullet value: TRUE
Back to the Outline
4 comments:
Remember, this is a wiki essentially. I will never get through this if I have to do all the research on my own. I picked this as the first one because it's relatively simple and clear-cut, but I still welcome argument, and especially new material. There is no reason why each section can't be several pages long.
You'd dig Mark D Schwartz. Geog prof at University of Wisconsin. Godfather of Phenology. Uses Remote Sensing alot, coined 'the Green Wave'. Cheers to your blog.
I did a quick read and admire what you've put together here. I would love to dig into a comprehensive reading list. Are you compiling a bibliography.
One question: are there data that show that fall is starting later? In crude sum, you have shared summaries of papers that provide strong evidence of changes in plant and animal life (I haven't read the papers, to be clear, so I am attempting only to characterize your summaries) that indicate primarily an earlier spring. Is that accurate? Or are you also saying that these papers suggest that the changes are manifested year-round (such as the often reported changes in polar bears and inbreeding with grizzlies)? If the data provided primarily talk about an earlier advent of spring, are they silent on fall trends as well?
Chris
At this point, the only bibliography I have are the papers listed on this post. I'm hoping for more, though! I found lots of papers dealing with one or two species but deferred to the meta-analyses as more indicative of a large-scale trend as opposed to a possible small-scale event.
Study 1 and study 2 deal with a lot more than just earlier springs. Phenology [the category which earlier springs is under] is one of the 4 change types cataloged in study 1 [the others being demographic, morphological, and genetic shifts]. Study 2 focused on demographic and phenological shifts. Study 3 focused only on phenology, mostly tracked through earlier springs.
So there is a wide base of data, only a fraction of which deals with earlier springs. However, you still have a great question: within phenology, why is it always "spring earlier?" and not "fall later?" My limited understanding is that fall is a lot more difficult to track and define than spring. Schwartz, for example, used sattelite surveys of leafing to measure the onset of spring. Leafing happens more abruptly than de-leafing [or whatever it would be called in the fall when deciduous trees lose their leaves]. Other phenological markers, such as egg-laying, are spring-only markers. The first two studies included some fall phenological markers, such as migration dates.
I wish I knew more about this, I'd love some input from anybody with more experience.
thanks for the comments!
Post a Comment