We usually associate reduction of carbon emissions with reduced consumption, as opposed to variation in timing of consumption, but this association is both too simplistic and also erroneous. Here is why: shifting more consumption activities toward periods of the day when energy generation mix is cleaner (e.g. daylight, when solar can be contributing more to the energy mix) can, quite literally, reduce overall emissions.
Right? Yep. Here is a nice piece of evidence from a natural experiment in Turkey. "In October 2016, Turkey chose to stay on DST all year round." This shifted a lot more consumption by the public from late afternoons to early mornings. As reported in Bircan, Cagatay and Wirsching, Elisa study "Daylight Saving All Year Round? Evidence from a National Experiment" (December, 2020, EBRD Working Paper No. 251, https://ssrn.com/abstract=3751336), overall levels of consumption did not change much, but "the policy has a strong intra-day distributional effect, increasing consumption in the early morning and reducing it in the late afternoon. This change in the load shape reduced generation by dirtier fossil fuel plants and increased it by cleaner renewable sources that can more easily satisfy peak load generation. Emissions from generation decreased as a result."
Overall, the authors "find that staying on DST during winter months may have led to a reduction in CO2 emissions of between 1,500 and 8,200 tons per day. Hence, the policy change has an unforeseen but beneficial effect of reducing greenhouse gas (GHG) emissions, as generation by “cleaner” power plants substitutes generation from “dirtier” ones to satisfy changes in intra-day demand."
Incidentally, the study does not appear to have considered the effects of solar in their study that should have increased the CO2 abatement effects. It is unclear to me as to why...