Global Rainfall

Has rainfall increased or decreased with rising temperatures? NCDC Daily contains the raw precipitation measurements from about 100,000 weather stations back to 1780. I put my computer  (iMAC-i7) to calculate this , but it took a week of CPU time!  Here are the results as compared to temperature anomalies.

Top graph is the change in the global annual average daily rainfall compared to a 30 year ‘normal’ value from 1961-1990 (i.e. Rainfall Anomaly) . The bottom graph compares this global average rainfall anomaly to the global average temperature anomaly (CRUTEM4 in blue) and my GHCN-DAILY in green.

Since 1975 global average rainfall on land has increased by about 1mm per day while simultaneously land average temperatures have risen by 1C. However, it appears that rainfall was equally high during the 19th century.

The calculation is similar to that used for GHCN-DAILY temperatures. Where possible I calculate for each station a normalised monthly rainfall between 1961-1990. I then use a 5 level icosahedral grid for averaging and also calculate the average (normal) monthly rainfall within each bin between 1961-1990.

It is very interesting to view how this ‘normal’ daily seasonal rainfall looks  on a 10242 node icosahedral grid. It shows beautifully how rainfall follows the sun. It may seem counter-intuitive but on average there is more rainfall during the summer months, than in those damp cold winter months.

Animation of the monthly averaged daily rainfall. Deep blue is >5mm/day. Light beige is < 0.02 mm/day

Ocean surfaces warm during summer months, thereby increasing evaporation which then drives rainfall.

The NCDC monthly rainfall ‘anomalies’ are plotted below.

The Global average daily rainfall ‘anomaly’ on land.

Could the observed increased rainfall between 1810 and 1870 perhaps be due to two extremely large volcanic eruptions – Tambora (1815) and Consiguina (1835)?  There is also a smaller rainfall peak immediately following Krakatoa (1883).

In general though a warmer world is a wetter world.

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UK Power Generation 2017-18

The balancing of energy supply with demand on the UK National Grid is performed by ELEXON and as a result they provide a live snapshot of the power generated to match that demand  by fuel type. I have been monitored this since December 2016. Peak demand in general occurs around 6pm and I use this value to compare the relative importance of different energy sources to energy security. The values provided by ELEXON  are for centrally ‘metered’ power supply and do not include smaller ‘feed-in’ sources. Feed in sources are mostly household solar panels, solar farms, and small wind farms. The University of Sheffield began estimating Solar power around the end of 2017 based on their regional insolation/capacity model. I have been monitored this solar value since the beginning of 2018. In addition unmetered ‘feed in’ wind farms are estimated to add ~46% to the larger metered wind farms. This correction is applied to the overall results below.

UK Power Generation at 6pm. The upper curve is the Peak Electricity Demand. The blue section combines French & NL imports with pumped storage and Hydro. (Click for full size version)

Peak demand in winter still exceeds 50GW despite energy saving measures. Nuclear Power provides a stable baseline of about 8GW. Coal generation remains essential to meet demand during winter months, however most of the bulk generation balancing is now met by Gas. Wind power is extremely variable, but remained strong this winter and contributed  an average 10.5% of peak demand or about 4.5GW. Maximum output at 6pm was ~12.5GW, while a record 14GW was recorded in the morning of March 17. This was also due to upgraded power transmission from Scotland to England. Solar Energy contributes essentially nothing during winter, and only becomes a significant factor after April and during daylight. Bio fuel has grown since 2016, but this growth is dominated by the DRAX turbines converting from burning coal to burning wood chips.

After November 2017 the demand curve is matched by the sum of all the fuel components, whereas before then there is an apparent small shortfall. I don’t have an answer as to why this is the case, but can only guess that the fuel figures were a little too low before November 2017. The Solar component apparently carries the supply of power beyond real time demand. That is because the effect of solar is to reduce the national demand curve through localised feed-in. However this ‘hidden’ solar is plotted here for comparison to the metered contributions from other fuels.

Erratic Wind

The week 31 May-5 June 2018 saw almost no wind across the UK, but instead a lot of sunshine. Here are the results for that week.

Power output from different fuels for the week 31 May – 5 June. From bottom to top Nuclear- Orange, Imports-purple, Hydro-cyan, Bio-brown,Red-coal, Gas-Pink, Wind-Green,Solar-Yellow

Total net Wind output fell as low as 0.05GW on Friday 1st June. Such lulls are not only restricted to Summer months. During the 2013/14 winter wind output fell below 0.2GW at 6pm on three separate occasions. For this reason the UK will need to keep in reserve an equal Gas capacity to that of all installed Wind farms simply to cover such lulls. Nor is it really feasible to store such huge amounts of energy. To cover one day without any wind (5GW) would need store 120GWh (430 TJ) of energy. This is 5 times larger than the bomb that destroyed Hiroshima. The largest Battery storage so far is the one that Elon Musk’s Tesla built in Southern Australia which can store 130MWh of Energy. Unfortunately this is a factor 1000 to small. The cost to the SA government for its installation was around  AUD 100 million. Nuclear power looks cheap in comparison!

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19th Century Volcanic Eruptions

There is clear evidence of a cooling effect in the GHCN-Daily data resulting from large volcanic eruptions during the 19th and 18th century.  If an eruption of a similar size to Tambora were to occur today it would (temporarily) cancel out all CO2 warming.

The severn largest volcanic eruptions in the last 270 years compared to Global Land Temperatures. The 3 largest eruptions all occurred before 1850. A comparison of GHCN-Daily with CRUTEM4 is shown in Green.

Note that early ‘Global’ temperatures are dominated by European stations. This is probably why Laki appears to be as strong as Tambora, which had a much larger effect in Asia.

Laki, Iceland – 1793 

Globally, those 95 Mt of sulphuric dioxide reacted with atmospheric water to form 200 Mt of sulphuric acid aerosols. Almost 90% of that sulphuric acid was removed in the form of acid rain or fogs, while 10% stayed aloft for over a year. This might explain why northern hemisphere temperatures were 1.3ºC below normal for 2-3 years after the eruption.  (Wired)

Tambora, Indonesia – 1815

Many volcanologists regard the Mount Tambora eruption as the largest and most-destructive volcanic event in recorded history, expelling as much as 150 cubic km (roughly 36 cubic miles) of ash, pumice and other rock, and aerosols—including an estimated 60 megatons of sulphur—into the atmosphere. As that material mixed with atmospheric gases, it prevented substantial amounts of sunlight from reaching Earth’s surface, eventually reducing the average global temperature by as much as 3 °C (5.4 °F). (Britanica)

Consiguina, Nicaragua, 1835

The January 1835 eruption of Cosigüina volcano, Nicaragua, ranks among the Americas’ largest and most explosive historical eruptions, but whether it had effects on global climate remains ambiguous. New petrologic analyses of the Cosigüina deposits reveal that the eruption released enough suphur to explain a prominent circa A.D. 1835 sulphate anomaly in ice cores from both the Arctic and Antarctic. A compilation of temperature?sensitive tree ring chronologies indicates appreciable cooling of the Earth’s surface in response to the eruption, consistent with instrumental temperature records. We conclude that this eruption represents one of the most important sulphur?producing events of the last few centuries and had a sizable climate impact rivaling that of the 1991 eruption of Mount Pinatubo. (Longpré et al.)

Krakatoa, Indonesia, 1883

In May 1883, the captain of the Elizabeth, a German warship, reported seeing clouds of ash above Krakatau. He estimated them to be more than 6 miles (9.6 km) high. For the next two months, commercial vessels and chartered sightseeing boats frequented the strait and reported thundering noises and incandescent clouds….On the morning of the 27th August, four tremendous explosions, heard as far away as Perth, Australia, some 2,800 miles (4,500 km) distant…… The explosions hurled an estimated 11 cubic miles (45 cubic km) of debris into the atmosphere, darkening skies up to 275 miles (442 km) from the Volcano…Within 13 days, a layer of sulphur dioxide and other gases began to filter the amount of sunlight able to reach Earth. The atmospheric effects made for spectacular sunsets all over Europe and the United States. Average global temperatures were as much as 1.2 degrees cooler for the next five years. (LiveScience)

By comparison the 20th century and the 21st century so far has seen far less Volcanic activity. Mount Pinatubu caused a temporary short term drop in global temperatures of about 0.4C for 2 years. Another Tambura type event would be far more serious with longer lasting effects. After-all we know how cold it can get at night!

Posted in Climate Change, climate science, UK Met Office | 9 Comments