On 27th February 1903 a major windstorm hit the UK and Ireland, known as Storm Ulysses.
The 20th Century Reanalysis (20CRv3) includes a modern reconstruction of the storm, created by assimilating available observations of surface pressure into a state-of-the-art weather forecast model.
There is a problem however. The number of available observations over north-west Europe is limited as most have never been digitised from the original hand-written paper sources. Recently, the WeatherRescue.org project rescued millions of observations, allowing us to examine the value of this new data by rerunning 20CRv3 with the new data added.
The animation below shows Storm Ulysses in the original version of 20CRv3 (left) and an improved version (right) with added observations (black dots). The contours are of sea level pressure and the colours are the wind speed at 10m, with blue arrows showing the wind vectors. The new rescued observations have reduced the minimum pressure, which is also simulated with more confidence.
But, is this an improvement? The wind ‘footprint’* for Storm Ulysses shows an increase in simulated wind speed when adding the new pressure observations, and this is now a far more credible simulation given the known damage that occurred during this storm (also see this photo).
* This figure shows the maximum wind speed from the 3-hourly simulated data so is probably an underestimate of the maximum sustained wind speed.
Would you like to be part of the UK registered rain gauge network? Do you have space to accommodate a rain gauge in your garden?
If you have a space in your garden or on your land for a rain gauge and time to record the rainfall each day, please read on… Continue reading WANTED: rainfall observers
It is not just air and ocean temperatures that are warming through climate change – the soils are warming too. At the University of Reading we have monitored underground temperatures every day since 1971 from 10cm to 100cm depth. There is a clear warming observed at each depth
The time series for 30cm depth can be extended back further to 1941 using observations from nearby sites – Maidenhead, Hurley and an older University campus (London Road*). The variations between overlapping site records are very consistent and more than 1.5°C warming has been observed overall in the last 80 years.
(Added 12th October 2019)
Data for other depths exists also. The seasonal cycle shows how different depths respond to the seasons, with deeper depths being lagged compared to the surface and smaller variations over the year. 10cm depth is coolest in the annual average, with 50-100cm being the warmest.
Graphics and analysis by Roger Brugge, University of Reading.
* Note the London Road campus is about 0.5°C warmer than the other sites, and this difference has been corrected for in the black line.
Following the ‘warming stripes‘ graphics for different locations around the world, this post focusses on the UK. The Met Office makes easily available long-running climate data from a small number of locations*. The visualisations below show the common changes in temperature and rainfall for the five longest climate monitoring stations in that set – Stornoway, Armagh, Durham, Sheffield & Oxford – which all have data for 1883-2017. Continue reading Climate stripes for the UK
Twenty years ago, the trend in annual mean global mean temperature became detectable. Ten years ago, regional seasonal mean temperature trends were becoming clear. Nowadays, we can see trends even in weather extremes. In this post I show trends in long-term meteorological station data for hot, cold and wet extremes, and share some thoughts on tropical cyclones and droughts. It is underpinned by a decade of studying these around the globe, often in collaboration with the WWA team. I make no claims for completeness: the world is large and complicated, and I simply do not know all the literature.
Guest post by Geert Jan van Oldenborgh
Continue reading Trends in extremes
The consequences of the Paris Agreement’s choice of the pre-industrial as its baseline have been discussed previously on this blog. This choice makes sense from a climate forcing perspective (as radiative forcings are measured with respect to a quasi-equilibrated state, and the well-observed recent past is not close to have finished responding to anthropogenic drivers). Looking back into the pre-industrial period, there are fewer instrumental observations of the temperature across the globe. So naturally our knowledge of the pre-industrial baseline temperature is uncertain.
Recent work, such as Hawkins et al. (2017) and Schurer et al. (2017), have looked to assess and quantify this uncertainty in light of future targets. The magnitude of this uncertainty, although small, becomes important when you consider the amount of warming left between today and the 1.5°C target. Continue reading Uncertainty in warming since pre-industrial times
Recent media headlines have again discussed the issue of whether climate models are overly sensitive to greenhouse gases. These headlines have misinterpreted a study by Millar et al. which was discussing carbon budgets to limit global temperature rise to 1.5°C above pre-industrial levels.
A recent study by Medhaug et al. analysed the issue of how the models have performed against recent observations at length and largely reconciled the issue. An overly simplistic comparison of simulated global temperatures and observations might suggest that the models were warming too much, but this would be wrong for a number of reasons. Continue reading Are the models “running too hot”?
For twenty years between 1883 and 1904, three intrepid weathermen lived at the top of Ben Nevis – the highest mountain in the UK – experiencing some of the worst weather the country has to offer.
Every hour, day and night, winter and summer, and whatever the weather, one of them would step outside and check the meteorological instruments, diligently recording the observations.
This was a uniquely Victorian-era endeavour. Science for the sake of science. Rather than exploring the world’s polar regions like some of their contemporaries, these Weathermen were exploring the atmosphere.
There was simply no other way of learning in detail about how the atmosphere changed with height without living at the top of a mountain. So that is what they did.
Continue reading Weathermen of Ben Nevis