Regional scale analysis of climate extremes in an SRM geoengineering simulation, Part 2: temperature extremes

In this study, we examine the statistics of temperature extremes in a model simulation of solar radiation management (SRM) geoengineering. We consider both intensity and frequency-based extreme indices for temperature. The analysis is performed over both large-scale domains as well as regional scales (22 Giorgi land regions). We find that temperature extremes are substantially reduced in geoengineering simulation: the magnitude of change is much smaller than that occur in a simulation with elevated atmospheric CO2 alone. Large increase (similar to 10-20 K) in the lower tails (0.1 percentile) of T-min and T-max in the northern hemisphere extra-tropics that are simulated under doubling of CO2 are reduced in geoengineering simulation, but significant increase (similar to 4-7 K) persist over high-latitude land regions. Frequency of temperature extremes is largely offset over land regions in geoengineered climate. We infer that SRM schemes are likely to reduce temperature extremes and the associated impacts on a global scale. However, we note that a comprehensive assessment of moral, social, ethical, legal, technological, economic, political and governance issues is required for using SRM methods to counter the impacts of climate change

Regional scale analysis of climate extremes in an SRM geoengineering simulation, Part 1: precipitation extremes

In this study, we examine the statistics of precipitation extreme events in a model simulation of solar radiation management (SRM) geoengineering. We consider both intensity and frequency-based extreme indices for precipitation. The analysis is performed over both large-scale domains as well as regional scales ( 22 Giorgi land regions). We find that precipitation extremes are substantially reduced in geoengineering simulation: the magnitude of change is much smaller than those that occur in a simulation with elevated atmospheric CO2 alone. In the geoengineered climate, though the global mean of the intensity of extreme precipitation events is slightly less than in control climate, substantial changes remain on regional scales. We do not find significant changes in the frequency of precipitation extremes in geoengineering simulation compared to control simulation on global and regional scales. We infer that SRM schemes are likely to reduce precipitation extremes and the associated impacts on a global scale. However, we note that a comprehensive assessment of moral, social, ethical, legal, technological, economic, political and governance issues is required for using SRM methods to counter the impacts of climate change

(Table A3) Raw irradiance values of glacier ice layer B (53-124 cm depth) from 350-900 nm (West Greenland)

This dataset contains the raw irradiance values that can be used to compute transmittance and attenuation coefficient, and are not interpolated or filtered, so the user can decide how to use the data

(Table A2) Optical attenuation coefficients of glacier ice layer A (12-77 cm ice depth) from 350-700 nm (West Greenland)

Formal estimates of attenuation coefficient for Layer A, interpolated to 1 nm resolution using a convolution (Savitsky-Golay) filter, and reported for the useable range of values, as described in the article

Optical attenuation coefficients of glacier ice from 350-700 nm and raw irradiance values from 350-900 nm

Optical attenuation coefficients of glacier ice from 350-700 nm were estimated from in-ice solar irradiance measured over the spectral range 350-900 nm and 12-124 cm depth collected at a site in the western Greenland ablation zone (67.15 oN, 50.02 oW). The acquired spectral irradiance measurements are used to calculate irradiance (flux) attenuation coefficients using an exponential decay Bouguer law model. Spectral absorption coefficients are estimated using the method of Warren et. al. (2006), which relates the attenuation coefficient to the absorption coefficient in the visible spectrum. The attenuation coefficients are calculated with linear regression between ice thickness in units of solid ice equivalent referenced to 917 kg/m3 and co-located transmittance. Solid ice equivalent thickness is calculated from in-situ ice density measured in the field on an ice core extracted from the measurement location. The ice density was 699 kg/m3 from 0-8 cm depth, 801 kg/m3 from 4-45 cm , 883 kg/m3 from 45-74 cm, and 888 kg/m3 from 74-122 cm. The depth-weighted ice density in the regions where attenuation was measured was 835 kg/m3 (12-77 cm) and 855 kg/m3 (53-124 cm). The field measurements were completed between 13:45 and 14:35 local time (UTC -3), at solar zenith angles of ~48–51o. Solar noon at this time and location is ~13:26

(Table A1) Optical attenuation coefficients of glacier ice layer B (53-124 cm ice depth) from 350-600 nm (West Greenland)

Formal estimates of attenuation coefficient for Layer A, interpolated to 1 nm resolution using a convolution (Savitsky-Golay) filter, and reported for the useable range of values, as described in the article

(Table A3) Raw irradiance values of glacier ice layer A (12-77 cm depth) from 350-900 nm (West Greenland)

This dataset contains the raw irradiance values that can be used to compute transmittance and attenuation coefficient, and are not interpolated or filtered, so the user can decide how to use the data