I was interested in a new paper which claims to be able to explain the Gaia hypothesis, first proposed by James lovelock, that life stabilises the earth’s climate. The paper is described in an article in the Conversation. The paper itself is here.
Life has existed on Earth for the last 3.7 billion years during which time the sun’s output has increased 30% while the atmospheric content has changed dramatically, determined by life and geology. Lovelock proposed a simple ‘Daisy World’ model of white and black daisies to illustrate how life could regulate temperature by changing surface albedo. This new paper takes this idea much further by generalising to an ensemble of species and environments. Each species is best adapted to a particular set of environmental parameters where they flourish and struggles far outside this optimum. Their interaction with the environment is such as to maintain these ideal set of conditions. The model assumes a Gaussian like distribution about these optimum conditions. There is then a competition between species, and external astronomy and geology which selects who survives and which species preferred environment wins out over time. They call this model “sequential selection”. It is illustrated in their Figure 1. below.
The figure shows a hypothetical interaction between 4 species as the environment changes (eg. Solar increases). Life acts to dampen change as 4 species flourish and then die off. Environmental variable E could simply be temperature.
This mechanism can only work if each species interacts with its environment so as to dampen changes from its preferred value, i.e. it has a negative feedback. If any Species evolves which globally has a positive feedback on an environmental variable, then it will quickly drive itself to extinction. This is where we find a bit of politics creeping into the article, because what is implied is that humans, despite our success, are nevertheless driving temperatures beyond the optimum value for our species.
What is true is that we are releasing a fraction of buried organic carbon back into the atmosphere over a relatively short time span, after which the atmosphere will slowly recover. The effect on climate and on other species will be negative in some places and perhaps even positive in others. As a result these other species will begin to react to these changes so as to counterbalance this increase in CO2. Plants are an obvious example.
I don’t think “sequential selection” is really a fundamental breakthrough in understanding Gaia. Instead it is more like an ensemble of ‘Daisy’ like species each with a Gaussian value for its optimum ‘environment’, whose populations acts to stabilises each successive optimum. If one fails (goes extinct) another then takes over, until (hopefully never) none are left and the planet dies.
Rainfall anomalies also have monthly spatial distributions analogous to those for temperature. North Atlantic storms in January 2014 brought flooding to Western England. That month’s distribution shows that abnormally high rainfall also affected the western coastlines of France, Spain and Portugal, the Alps and Eastern Europe.
Rainfall “daily” anomalies in mm for Jan 2014. The Western coastline of Europe, the Alps and Russia all had exceptional rainfall.
Here is an animation of average rainfall anomalies from Jan 2014 to March 2018. The distribution of abnormal “wet areas” is not random but instead flows with the seasons.
Precipitation anomalies from Jan 2014 to March 2018
Colour Scale in mm/day for each month.
Only the darker blue spots are significantly wetter than the 30 year average (1961-1990). Light blue to yellow areas are all dryer than normal.
Finally we look at the old data from 1838 to 1860 which gives a strong positive ‘global’ rainfall anomaly in the annual data. The values are in reality very regional, as are those for temperature anomalies.
Animation of the early precipitation data showing that it was dominated by Europe with just a few stations in the US and Australia.
The early stations are sparsely distributed mainly in central Europe, US & Australia. They indeed show mainly positive rainfall anomalies. It would seem that these areas were actually wetter than today, but just how reliable these trends are is unclear. Perhaps the rain gauges or procedures were less accurate than they are today.
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.