Category Archives: Precipitation

Bias in historical England and Wales precipitation data

Conor Murphy, Robert L. Wilby, Tom, K.R. Matthews, Peter Thorne, Ciaran Broderick, Rowan Fealy, Julia Hall, Shaun Harrigan, Phil Jones, Gerard McCarthy, Neil Macdonald. Multi‐century trends to wetter winters and drier summers in the England and Wales precipitation series explained by observational and sampling bias in early records. International Journal of Climatology, https://doi.org/10.1002/joc.6208

Globally, few precipitation records extend to the 18th Century. The England Wales Precipitation (EWP) series is a notable exception with continuous monthly records from 1766. EWP has found widespread use across diverse fields of research including trend detection, evaluation of climate model simulations, as a proxy for mid‐latitude atmospheric circulation, a predictor in long‐term European gridded precipitation datasets, the assessment of drought and extremes, tree‐ring reconstructions and as a benchmark for other regional series. A key finding from EWP has been the multi‐centennial trends towards wetter winters and drier summers. We statistically reconstruct seasonal EWP using independent, quality‐assured temperature, pressure and circulation indices. Using a sleet and snow series for the UK derived by Profs. Gordon Manley and Elizabeth Shaw to examine winter reconstructions, we show that precipitation totals for pre‐1870 winters are likely biased low due to gauge under‐catch of snowfall and a higher incidence of snowfall during this period. When these factors are accounted for in our reconstructions, the observed trend to wetter winters in EWP is no longer evident. For summer, we find that pre‐1820 precipitation totals are too high, likely due to decreasing network density and less certain data at key stations. A significant trend to drier summers is not robustly present in our reconstructions of the EWP series. While our findings are more certain for winter than summer, we highlight i) that extreme caution should be exercised when using EWP to make inferences about multi‐centennial trends, and; ii) that assessments of 18th and 19th Century winter precipitation should be aware of potential snow biases in early records. Our findings underline the importance of continual re‐appraisal of established long‐term climate datasets as new evidence becomes available. It is also likely that the identified biases in winter EWP have distorted many other long‐term European precipitation series.

2019 the coldest/wettest January-June on record in the US

“Sixty-nine percent of the US has averaged below normal temperature this year, with thirty-four percent more than two degrees below normal.” click here

Has Himalayan glacier melting doubled?

“A newly comprehensive study shows that melting of Himalayan glaciers caused by rising temperatures has accelerated dramatically since the start of the 21st century,” claims a Ph.D. candidate at Columbia University’s Lamont-Doherty Earth Observatory. Willis Eschenbach shares his thoughtsclick here

Dry summers come and go

“We aren’t the first scientists to confirm this trend,” says Dr. Tobias Scharnweber, one of the authors of the article. “However, what is new in our reconstruction is that we were able to calculate these growth rates using our own data method that we had developed especially for this project. This enabled us to show that average summer rainfall amounts were much lower at the time of the Mediaeval Climate Optimum, i.e. approximately 1000 years ago, than previously presumed. Maybe ‘one-in-a-century’ summers, like the one we had in 2018, were not that rare back then.” click here

Tobias Scharnweber, Karl-Uwe Heußner, Marko Smiljanic, Ingo Heinrich, Marieke van der Maaten-Theunissen, Ernst van der Maaten, Thomas Struwe, Allan Buras & Martin Wilmking . Removing the no-analogue bias in modern accelerated tree growth leads to stronger medieval drought. Scientific Reports, volume 9, Article number: 2509 (2019).

In many parts of the world, especially in the temperate regions of Europe and North-America, accelerated tree growth rates have been observed over the last decades. This widespread phenomenon is presumably caused by a combination of factors like atmospheric fertilization or changes in forest structure and/or management. If not properly acknowledged in the calibration of tree-ring based climate reconstructions, considerable bias concerning amplitudes and trends of reconstructed climatic parameters might emerge or low frequency information is lost. Here we present a simple but effective, data-driven approach to remove the recent non-climatic growth increase in tree-ring data. Accounting for the no-analogue calibration problem, a new hydroclimatic reconstruction for northern-central Europe revealed considerably drier conditions during the medieval climate anomaly (MCA) compared with standard reconstruction methods and other existing reconstructions. This demonstrates the necessity to account for fertilization effects in modern tree-ring data from affected regions before calibrating reconstruction models, to avoid biased results.

“Climate science” snow predictions are unreliable, not science-based

California stations show no precipitation trend change for prior 30 year period

“As we can see, there has been no trend over the past 30 years. Variability also appears unchanged. California has always been a state characterized by alternating periods of drought and rainfall influenced by oceanic cycles like ENSO. The data show everything is within the normal range.” click here

Rainwater Harvesting in a Subarctic Community

Mercer N, Hanrahan M. Straight from the heavens into your bucket”: domestic rainwater harvesting as a measure to improve water security in a subarctic indigenous communityInternational journal of circumpolar health. 2017;76(1):1312223. doi: 10.1080/22423982.2017.1312223

BACKGROUND: Black Tickle-Domino is an extremely water-insecure remote Inuit community in the Canadian subarctic that lacks piped-water. Drinking water consumption in the community is less than a third of the Canadian national average. Water insecurity in the community contributes to adverse health, economic, and social effects and requires urgent action.

OBJECTIVES: To test the ability of domestic rainwater harvesting (DRWH) for the first time in the subarctic with the goal of improving water access and use in the community.

DESIGN: This project utilised quantitative weekly reporting of water collection and use, as well as focus group discussions. DRWH units were installed at seven water-insecure households chosen by the local government. Results were measured over a 6-week period in 2016.

RESULTS: Participants harvested 19.07 gallons of rainwater per week. General purpose water consumption increased by 17% and water retrieval efforts declined by 40.92%. Households saved $12.70 CDN per week. Participants reported perceived improvements to psychological health. Because no potable water was collected, drinking water consumption did not increase. The study identified additional water-insecurity impacts.

CONCLUSION: DRWH cannot supply drinking water without proper treatment and filtration; however, it can be a partial remedy to water insecurity in the subarctic. DRWH is appropriately scaled, inexpensive, and participants identified several significant benefits.