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Spring Temperatures & First Flowering Dates In The UK

October 28, 2016

By Paul Homewood  




My attention was drawn to the above paper today which was originally published in 2010. As the title infers, it investigated first flowering dates in the UK, and came to the conclusion that flowering has been getting earlier, as temperatures in February to April have increased.    

This is the Abstract:


Widespread concerns about global biodiversity loss have led to a growing demand for indices of biodiversity status. Today, climate change is among the most serious threats to global biodiversity. Although many studies have revealed phenological responses to climate change, no long-term community-level indices have been developed. We derived a 250-year index of first flowering dates for 405 plant species in the UK for assessing the impact of climate change on plant communities. The estimated community-level index in the most recent 25 years was 2.2–12.7 days earlier than any other consecutive 25-year period since 1760. The index was closely correlated with February–April mean Central England Temperature, with flowering 5.0 days earlier for every 1°C increase in temperature. The index was relatively sensitive to the number of species, not records per species, included in the model. Our results demonstrate how multi-species, multiple-site phenological events can be integrated to obtain indices showing trends for each species and across species. This index should play an important role in monitoring the impact of climate change on biodiversity. Furthermore, this approach can be extended to incorporate data from other taxa and countries for evaluating cross-taxa and cross-country phenological responses to climate change.



The key graph, which tells the story, is this one:



Figure 1.

The median (red line) and 95% credible intervals (grey area) of the estimated community-level index (day of the year) showing a temporal change in the timing of first flowering shared by 405 plant species observed throughout the UK. The black line indicates the mean for every 25 years and the dotted line that for the most recent 25 years. The years without estimates indicate those without any observation records (1766, 1813, 1814 and 1817).


As the index value falls, this indicates earlier flowering.

We can see how flowering has moved forwards in the last 25 years. But what is clear is that we are not seeing a simple, straight trend.

In particular, there is very little difference between the current period and that of 1910 to 1934. In between, there is a period of much later flowering. It is also noticeable that flowering was relatively early during the first 25-year period in the 18thC, followed by a persistent trend to later flowering up to the mid 19thC (although error margins are much larger in those earlier years)..


In fact, there should be very little surprise about this, as HH Lamb wrote about the subject in 1982, in “Climate, History and The Modern World”:





Lamb was clear that growing seasons were significantly shorter in the 1960s and 70s, than they were a few decades earlier, largely due to colder springs.

But note the comment about Oxford, that onset of spring was 16 days earlier compared to the 1920-50 period. This is a much bigger difference than the one showing in the Amano paper – they suggest something like only six days.

This surely reinforces the contention that there is actually very little difference between now and that earlier 20thC era. 

  1. Joe Public permalink
    October 28, 2016 6:45 pm

    A number of botanical papers recognise and draw attention to the fact that urban heat islands have affected flowering dates. Particularly as UHIs tend to increase night-time temperatures.

    For example …..

    Click to access asset

    • Mike Jackson permalink
      October 28, 2016 6:58 pm

      A lot more work needs to be done on both the UHI effect and the extent to which average temperatures have been affected by increased minima rather than increased maxima.

      Since both these aspects of global warming have the potential to kill the golden goose stone dead don’t look for any in-depth analysis from the climastrologists any time soon.

  2. Broadlands permalink
    October 28, 2016 7:15 pm

    Here is another paper on the UHI….

    Click to access 2007-65-2-climate-change-and-cherry-tree-blossom-festivals-in-japan.pdf

    Excerpt… “cherry tree flowering times have been strongly influenced by the urban heat island effect, the warming that comes from the added heating caused by removing trees and replacing them with roads, parking lots, buildings and other aspects of a human-dominated landscape. In studies of the impact of global warming, it is important to separate the effects of localized warming caused by urbanization from the more general aspects of warming caused by global climate change.”

    And there are others….

  3. October 28, 2016 7:16 pm

    There is a similar picture with winter temperatures, the last 25 years have been relatively free of the severe winters of the past, but 2010/11 indicated that this relatively mild period may be about to end:

    • Broadlands permalink
      October 28, 2016 7:53 pm

      In the US 48 states, according to NOAA’s data, the winters (DJF) have been getting colder since 1998 at the rate of -0.78°F per decade.

    • John F. Hultquist permalink
      October 30, 2016 4:47 am

      Patterns shift. The winters of 2013/2014 and 2014/2015 were very cold in parts of North America. Here is a report from Michigan with a map showing the adjacent parts of several states and of Ontario.

  4. JLC permalink
    October 28, 2016 7:48 pm

    More interesting is that the period which looks like 1758-1783 was nearly as early flowering as the current 25 yr period. Without UHI nor 400 ppm CO2 !

  5. October 28, 2016 7:55 pm

    Reblogged this on WeatherAction News.

  6. October 28, 2016 8:02 pm

    Possible mechanism of abrupt jump in winter surface air temperature in the late 1980s over the Northern Hemisphere, Kim et al

  7. October 28, 2016 8:23 pm

    Went and read the paper. Not very impressed. Tried to smush discontinuous records from different places (UK latitude) of 405 species (some with multiple records from multiple places, others not) having widely differing flowering dates into a community level index using heirarchical models and Bayasian statistics. This is one area where Bayes theorem does not apply well. The index is a statistical hash that they tried to pretend was robust because they could reproduce it more or less with random subsets (75%, 50%, 25%) of the records. Sure, since their statistical sausage machine makes sausage the same way every time. The global warming alarm at the beginning and end of the paper bears little to no relationship to the actual result fugure 2–flowering is earlier when CET spring is warmer, but with a lot of noise–or the figure from the paper in the post. This paper is statistically about as junky as it gets.

  8. tom0mason permalink
    October 28, 2016 8:45 pm

    When such a large subject as vegetative abundance or decline over time are to be assessed, all the natural and manmade variation must be taken into consideration.

    In as much as times of flower blooming, and plant growth etc. can indicate long term changes, it must be noted that in the short term, variation are also caused by the previous years’ rain, total amount of sunshine, disease infections, and pest predation. Some of these stressors can cause a sudden abundance or a rapid decline in particular plants.

    In the long term there are many changes in land use to take into account over the time period as well as the climate variations. The huge tracts of urbanization (and its local urban heat island effect) of what was once open, and relatively wild countryside must be accounted for. That and the technological industrialization of agriculture, all the changes in food plant breeds and varieties, and changes in the type and use of pesticides. In the past two century or so, huge numbers of imported plants, with new and diverse array of pests, diseases and microbial contaminants have arrived, and will have an effect. We now intensively grow more food on less land than ~150 years ago. All of this will have effects that ripple out to the rest of the native flora and fauna of the country. Today’s skys and atmosphere are, in many localities, cleaner and clearer now than in the industrial heydays, or during those periods of European conflicts of the world wars.

    H.H. Lamb seems to have a better attitude towards how to regard these changes in the short term.
    This latest study appears to try to explain the long term changes that have happened as being the result of atmospheric temperature change when actually so many other parameters have changed. I feel they are missing too much.

  9. kuhnkat permalink
    October 28, 2016 10:35 pm

    CO2 generally increases the plants growth, not just size but how fast. CO2 also allows the plants to have smaller stomata decreasing loss of moisture and increasing its ability to control its optimum temps. Altogether it should be unsurprising that the increase in CO2, even with fixed temps, would allow earlier flowering dates.”

    “Carbon dioxide (CO2) is an essential component of photosynthesis (also called carbon assimilation). Photosynthesis is a chemical process that uses light energy to convert CO2 and water into sugars in green plants. These sugars are then used for growth within the plant, through respiration. The difference between the rate of photosynthesis and the rate of respiration is the basis for dry-matter accumulation (growth) in the plant. In greenhouse production the aim of all growers is to increase dry-matter content and economically optimize crop yield. CO2 increases productivity through improved plant growth and vigour. Some ways in which productivity is increased by CO2 include earlier flowering, higher fruit yields, reduced bud abortion in roses, improved stem strength and flower size. Growers should regard CO2 as a nutrient.”

  10. October 28, 2016 10:43 pm

    The climate changes naturally and the big change is in winter spring and autumn. Until all the sources of change are understood and quantified humanity will suffer from the activity of the witch doctor element who try and maintain that the globe is overheating even though summer temperatures are unchanged.

    This seems apt: “It would not be impossible to prove with sufficient repetition and a psychological understanding of the people concerned that a square is in fact a circle. …

    • Broadlands permalink
      October 29, 2016 2:05 pm

      Erl… We are naive to think that if and when things are actually understood that the “witch doctor element” will stop trying to make us conform to the absurd effort to control the climate by massive “negative emission” ventures that are totally hopeless. “They” are crying FIRE in an increasingly crowded “theater” with no Fire Department nor any realistic way to put out a forecasted?? “fire”. As Gavin, NASA’s current leader and “enforcer” just said: “we won’t ever see a month below 400 ppm”. His predecessor agreed: “wishful thinking”. But the “beat goes on” and the scary forecasts will continue.

    • October 30, 2016 2:23 am

      +erl happ, as Robert Herritt wrote in New Atlantis, we humans are prone to think that the best beliefs are those that exhibit the best moral values and virtues. Aristotle said that the most virtuous shape is a circle, so your suggestion is not as absurd as it might seem.

      Settledscience settledscience settledscience settledscience settledscience settledscience settledscience settledscience settledscience settledscience settledscience settledscience and so on ad infinitum.

  11. John F. Hultquist permalink
    October 29, 2016 3:38 am

    “… climate change is among the most serious threats to global biodiversity.

    This is a stupendously stupid rumor.
    Global warming is supposed to warm high latitudes more than equatorial regions. Biodiversity seems to be decreased in those high latitudes so a little warming ought to improve things. Further, a changing environment is believed to encourage changes in life forms so we might expect to see new, and maybe improved, models of things. Whether there might be more or less of anything is technically called a WAG.

  12. Athelstan permalink
    October 29, 2016 11:10 am

    ristvan has it and exactly.

    This [paper] is a jaunt, of pure speculative extrapolation with added mythical climatastrophe all thrown in, where the paper’s statistical analysis is woeful, even schoolboy stuff.

    Anecdotal stuff, during recent UK springtime temperature variation has been pretty large by UK standards – 2013 FEB/MAR and the daffs were just losing their sparkle in late MAY!….yes it was particularly cold [for Britain not by world standards] – however, Jan,Feb, Mar 2016 mild and wet and about the par and daffs were gone by the commencement of April. We are after all, in a maritime climate region. Warmer waters lapping further north, no doubt have been a factor in milder winters, that is not in dispute and in all likelihood winters will return to being far more severe – even in Britain – that’s a fact.

    We are so very lucky here in Britain we have the Atlantic conveyor sweeping a current and warm sweet winds [Coriolis too] up from the Caribbean basin and we are surrounded by relatively warm seas, thus we are blessed. Unless and always possible from Iceland, some large volcanic eruption occurs notwithstanding a ‘Polar Vortex’ whatever that new phenomena is, Britain I hope will remain as it always has during the most recent interstitial – warmish, coolish, dryish, occasionally quite hot and sometimes quite cold – not bad for a latitude of 50º + N!

    Now bring on the sun!

    • John F. Hultquist permalink
      October 30, 2016 2:52 am

      ” we have the Atlantic conveyor sweeping a current and warm sweet winds [Coriolis too] up from the Caribbean basin”

      The Source of Europe’s Mild Climate”
      The notion that the Gulf Stream is responsible for keeping Europe anomalously warm turns out to be a myth

      Gulf Stream – Not

  13. john cooknell permalink
    October 29, 2016 7:36 pm

    What about the effect of urban lighting, you can clearly see the effect street lighting has on vegetation at both Spring and Autumn, the plants nearest to the street lights bud first and lose their leaves last

  14. October 30, 2016 2:42 am

    The paper says

    Since the number of species and records per species included in the model vary greatly throughout the period considered

    To an ignoramus like myself that sounds almost like, “biodiversity has always changed and will continue to change.”

    Where I live, spring arrived about three weeks later this year than it has done in some previous years. That’s a pretty big year-on-year variation. The masked weavers had already changed to their breeding plumage, and didn’t seem to be put out at all.

    • daveR permalink
      October 30, 2016 7:14 am

      There are endless discussions amongst us Scots salmon fishers about seasonality. What appears obvious is the relationship between NA cooling and spring fish numbers: when the NA turns cooler, early season numbers are there and vice-versa. It’s mighty difficult to strip out other key factors – discharge/effort etc. The presumed late Tony George did a whack of work on salmon stats til early90s; his conclusion was that single winter (1SW) fish were precursory to 2SW salmon (the norm).

      Here’s my point: IFF the NA undergoes a quasi-cyclical 60yr warming/cooling cycle then seasonal runs seem to pattern in very closely to both catches and perceived abundance. Sure, we’ve got the long-term river flow data and declared catch but zero meaningful in terms of effort largely making any analysis moot. What appears clear, however, via Ole Humlum, is that the NA has been cooling since 2007 and early-running fish are increasingly back in northern Scottish waters. My fifty quid bet to a pal is that it’s cooling and springers will return in numbers.

      We’ll see…

  15. Roy Hartwell permalink
    October 30, 2016 4:08 pm

    Christmas 1836 ‘Mild weather continued and in Berrynarbor wild flowers were picked including cranesbill, dandelion, strawberry, groundsel, fumitory, blackberry, feverfew, white nettle, periwinkle, daisy, primrose, thistle, hemlock, veronica and violets ‘ Christmas 1845 ‘ A boquet of primroses was picked at Whitestone near Exeter ‘ Christmas 1849 ‘ After a period of sharp frosts, Christmas Day was warm and sunny followed shortly afterwards by a severe snowstorm in which ten inches of snow fell,. 1866 ‘ A wild strawberry was picked on Christmas Day in Black Torrington’. 1871 ‘ Primroses were picked at Ipplepen’. All from Devon County Records !!!!


  1. British Climate History: 250 Years Of Spring Temperatures & First Flowering Dates In The UK | The Global Warming Policy Forum (GWPF)

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