CO2 levels were a very safe 280 ppm.
The Great Storm of 1703 is arguably the most severe storm or natural disaster ever recorded in the southern part of Britain. It affected southern England and the English Channel. A 120-mph (193-km/h) perfect hurricane, it started on 24 November, and did not die down until 2 December 1703.
Observers at the time recorded barometric readings as low as 973 millibars (measured by William Derham in South Essex) but it has been suggested that the storm may have deepened to 950 millibars over the Midlands.
Temperatures during that time were sometimes cold enough to freeze over the Thames. Apparently the low CO2 levels loaded the dice for extreme weather.