the Spörer Minimum is actually some 50 years earlier. A 50-year response lag is possible but is not consistent with subsequent variations in inferred solar activity and average northern hemisphere temperature. For example the peak in solar activity between the Spörer Minimum and the Maunder Minimum is 50 years after the only peak in average northern hemisphere temperature that it could be associated with. A study by Judith Lean in 1999 also pointed to a relationship between the sun and the Little Ice Age. Her research found that there was a 0.13% total solar irradiance (TSI) increase () over 1650–1790 which could have raised the temperature of the earth by 0.3 °C. In the calculated correlation coefficients of the global temperature response to their reconstruction of the solar forcing over three different periods, they found an average coefficient of 0.79 (i.e. 62% of the variation could be explained by the TSI) which indicates a possible relationship between the two components. Lean's team also formulated an equation in which the temperature change is 0.16 °C increase in temperature for every 0.1% increase in total solar irradiance. However, the main problem with quantifying the longer-term trends in TSI lies in the stability of the absolute radiometry measurements made from space, which has improved since the pioneering work of Judith Lean discussed above, but still remains a problem. Analysis comparing trends in modern observations of TSI and cosmic ray fluxes shows that the uncertainties mean that it is possible that TSI was actually higher in the Maunder Minimum than present-day levels, but uncertainties are high with best estimates of the difference between the modern-day TSI and the Maunder-Minimum TSI in the range ± but with a uncertainty range of ± At the center of the LIA, during the Spörer Minimum and the Maunder Minimum, sunspots were minimal and cosmogenic isotope deposition (carbon-14 and beryllium-10) was increased in these minima as a result. However, detailed studies from multiple paleoclimate indicators show that the lower Northern Hemisphere temperatures in the Little Ice Age began before the start of the Maunder Minimum but after the start of the Spörer Minimum and persisted until after the Maunder Minimum (and even after the much weaker Dalton Minimum) had ceased. The return to more active solar conditions between these two grand solar minima had no obvious effect on either global or Northern Hemisphere temperatures. The Central England Temperature provide