Climate

Decades Of Data Show Spring Advancing Faster Than Experiments Suggest

“This suggests that predicted ecosystem changes — including continuing advances in the start of spring across much of the globe — may be far greater than current estimates based on data from warming experiments.”

From NASA’s Goddard Institute for Space Studies

Plants are leafing out and flowering sooner each year than predicted by results from controlled environmental warming experiments, according to data from a major new archive of historical observations assembled with the help of a NASA researcher.

Researchers use experiments that manipulate the temperature of the environment surrounding small plots of plants to gauge how specific plants will react to higher temperatures. The observed plant responses can then be incorporated into models that predict future ecosystem changes as temperatures around the globe continue to rise. But when a group of scientists compared these results to a massive new archive of historical observations, they found that the warming experiments are dramatically underestimating how plants respond to climate change.

The results were published online in the journal Nature on May 2. In addition to quantifying how a broad collection of plant species have responded to date to rising temperatures, the study suggests that the way warming experiments are conducted needs to be re-evaluated.

“This suggests that predicted ecosystem changes — including continuing advances in the start of spring across much of the globe — may be far greater than current estimates based on data from warming experiments,” said Elizabeth Wolkovich, who led the interdisciplinary team of scientists behind the new research while she was a postdoctoral fellow at the University of California, San Diego. “The long-term records show that phenology is changing much faster than estimated based on the results of the warming experiments. This suggests we need to reassess how we design and use results from these experiments.”

Benjamin Cook, of NASA’s Goddard Institute for Space Studies and Columbia University, New York, worked with Wolkovich to create the massive new archive of long-term, natural phenology observations to gauge the accuracy of the phenological predictions based on these plant warming experiments. The archive includes data from 1,558 species of wild plants on four continents. The historical records showed that leafing and flowering will advance, on average, five to six days per degree Celsius — a finding that was consistent across species and datasets. These data show that estimates based on data from warming experiments are underpredicting advances in flowering by eight and a half times and advances in leafing by four times. The authors expect the data archive to be an important benchmark in future phenology studies.

“These results are important because we rely heavily on warming experiments to predict what will happen to ecosystems in the future,” said Cook, who helped bring together a research team including support from the National Center on Ecological Analysis and Synthesis to build the archive of real-world observations. “With these long-term observational records you may be able to pick up a shift in a plant community over a few years that you wouldn’t be able to observe in an experiment.”

The study of phenology, the timing of annual plant events such as the first flowering and leafing out of spring, provides one of the most consistent and visible responses to climate change. Long-term historical records, some stretching back decades and even centuries, show many species are now flowering and leafing out earlier, in step with rising temperatures. Because these records aren’t available everywhere and predicted future warming is often outside the range of historical records, ecologists often use controlled experiments that create warmer conditions in small plots to estimate how different species will respond to expected temperature increases.

The timing of plants’ flowering and leafing out in spring is not only a basic, natural indicator of the state of the climate. Predicting plant responses to climate change has important consequences for human water supply, pollination of crops and overall ecosystem health.

Wolkovich, Cook and colleagues suggest a number of potential reasons the estimates based on experimental data have underpredicted the plant response to higher temperatures. There could be additional effects of climate change not mirrored in the controlled experiments, or from the fact that the methods used to create warmth in the studies could be creating counteracting effects such as drying out soils or reducing the amount of sunlight reaching the plants.

“Continuing efforts to improve the design of warming experiments while maintaining and extending long-term historical monitoring will be critical to pinpointing the reasons for the differences, and will yield a more accurate picture of future plant communities and ecosystems with continuing climate change,” Wolkovich said.

This research was originally published at NASA’s Goddard Institute for Space Studies. The study is here (subs. req’d).

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14 Responses to Decades Of Data Show Spring Advancing Faster Than Experiments Suggest

  1. Zan says:

    Wow, Joe! hat’s a great article re: how they do the experiments on phenology. much needed analysis. Thanks.

  2. Paul Magnus says:

    Not only are they starting earlier, but spring and fall are going to be getting shorter. We will only have 2 seasons at some point. This might be a trigger for feedbacks. Maybe a negative one…

  3. BBHY says:

    Maybe it is not only the change in temperature but also changes in rainfall patterns and atmospheric CO2 levels?

  4. Joy Hughes says:

    What about the extra IR coming from all over the sky, like a giant heat lamp? It seems like this would affect plants in partial shade more than warmer average temps…

  5. Joan Savage says:

    The article abstract includes, “We show that warming experiments underpredict advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold, respectively, compared with long-term observations.”

    That’s a serious amount of under-prediction.

    The article authors commented that the discrepancy could be due to remediable limitations of the experiments, but they also include the possibility of “complex interactions among multiple drivers in the observational data.”

    All those possibilities are worth more lengthy comments.

  6. Mulga Mumblebrain says:

    Perhaps the researchers err on the side of caution,lest they be smeared as ‘alarmists’.

  7. Merrelyn Emery says:

    Yet another demonstration to our mainstream science community that their linear, mechanistic conceptualization of the world is wrong. The world consists of open systems where a change in the environment or any part affects every part and the whole. That is why the predictions from the experiments and modelling are always underestimates.

    There is nothing new about systems theory but it seems that even now, on the brink, most of our scientists refuse to acknowledge that they are out of touch with reality and clinging to a myth. They are doing us all a grave diservice, ME

  8. Dennis Tomlinson says:

    Maybe mother nature is a complex, non-linear, self-adaptive system. Maybe we don’t know enough to predict the stimulus-response to a warming climate.

  9. Tim says:

    Perhaps that is why one does such experiments – wherein variables are systematically and “mechanistically” varied – otherwise, the nonlinearities can’t be properly understood. I suspect that these members of the “mainstream science community” have a vastly more complex “conceptualization” of the world than your cartoonish characterization would suggest.

    If you think it is the scientific community that is out of touch with reality, you may be the one doing us a grave disserivice.

  10. Merrelyn Emery says:

    Oh dear! Tim, it is impossible to ‘properly’ understand the nonlinearities by varying one or a very few variables at a time in an artificial environment. In real environments, all variables change as a result to a change in one or more variables. I can give you example after example where the reductionist approach not only failed to give a good approximation of the real result but caused drastic consequences for the living systems involved. In some cases, the variables so well understood in isolation or in the lab, behaved in exactly the opposite way when inserted into a whole system such as a human body or a living ecosystem. These examples are not mistakes or freakish incidences. Like the example which is the subject of this article they should educate us about the reality of our world and how to better conduct our research, ME

  11. Tim says:

    You’ve missed the point. Before conducting the experiments that you’ve criticized, we/they didn’t know that they wouldn’t capture the the most important variables involved in advancing Spring dates. The failure of the experiments to do that tells us something – as Dennis Tomlinson remarked below, “Maybe we don’t know enough to predict the stimulus-response to a warming climate.” I doubt that any serious scientist working in this field imagines that their experiments will be the ‘final word’ on the subject. You seem to be making the assumption that they do suffer from that misapprehension and, if so, your assumption is unwarranted.

  12. Joan Savage says:

    It is desirable to have a fuller understanding of all CC stressors on plants.

    For example, earlier bloom and earlier leaf out can be adaptations to grazing stress, which occurs when there is low snow cover and herbivores can move freely in mild winters.

    Further, it would be a good experiment also to see if the more stochastic unpredictable weather conditions of climate change are themselves a stressor, even while the average increase in temperature is in the background. Pulses of warm days and cold, wet and dry, can stimulate many organisms into strategies like early reproduction and more rapid tissue replacement.

    For a grim comparison to humans, war-torn Afghanistan has one of the highest birthrates in Asia, as well as one of the shortest average life-spans, along with many child-brides, pushing their ‘flowers’ to bloom early.

  13. Joan Savage says:

    Amplifying feedbacks can occur on multiple physical scales and in nested or linked time-frames.

  14. Merrelyn Emery says:

    Tim, the basic assumption I make is that the world behaves the way it has long been observed to behave, i.e. systemically. It does not function as a collection of independent variables that may or may not interact in some way.

    To continue to assume the latter in the face of what is now a long series of serious underestimates of the effects of warming is not only a failure of conceptualization: it also reveals an ideology. The history of science is littered with the ghosts of ideologies which failed to adequately describe or explain reality. Fortunately, we still have careful observational studies that can redirect our conceptualizations and research methods in this area, ME