When the IPCC began to produce its IPCC Sixth Assessment Report, many climate models began to show a higher climate sensitivity. The estimates for Equilibrium Climate Sensitivity changed from 3.2 °C to 3.7 °C and the estimates for the Transient climate response from 1.8 °C, to 2.0 °C. That is probably because of better understanding of the role of clouds and aerosols. Methods of estimation Using Industrial Age (1750–present) data Climate sensitivity can be estimated using the observed temperature increase, the observed ocean heat uptake, and the modelled or observed radiative forcing. The data are linked through a simple energy-balance model to calculate climate sensitivity. Radiative forcing is often modelled because Earth observation satellites measuring it has existed during only part of the Industrial Age (only since the mid-20th century). Estimates of climate sensitivity calculated by using these global energy constraints have consistently been lower than those calculated by using other methods, around or lower. Estimates of transient climate response (TCR) that have been calculated from models and observational data can be reconciled if it is taken into account that fewer temperature measurements are taken in the polar regions, which warm more quickly than the Earth as a whole. If only regions for which measurements are available are used in evaluating the model, the differences in TCR estimates are negligible. A very simple climate model could estimate climate sensitivity from Industrial Age data by waiting for the climate system to reach equilibrium and then by measuring the resulting warming, (°C). Computation of the equilibrium climate sensitivity, S (°C), using the radiative forcing (W/m2) and the measured temperature rise, would then be possible. The radiative forcing resulting from a doubling of , , is relatively well known, at about 3.7 W/m2. Combining that information results in this equation: . However, the climate system is not in equilibrium since the actual warming lags the equilibrium warming, largely because the oceans take up heat and will take centuries or millennia to reach equilibrium. Estimating climate sensitivity from Industrial Age data requires an adjustment to the equation above. The actual forcing felt by the atmosphere is the radiative forcing minus the ocean's heat uptake, (W/m2) and so climate sensitivity can be estimated: The global temperature increase between the beginning of the Industrial Period, which is (taken as 1750, and 2011 was about . In 2011, the radiative forcing from and other long-lived greenhouse gases