Emerging capabilities in satellite observations of the atmosphere that will decrease uncertainty in quantifying global warming

The dangers of global warming have not been fully met with measures to mitigate them, because it is difficult to match uncertain concerns with concrete steps, especially when it requires international cooperation at the highest levels. The large uncertainty of the magnitude of global warming is dominated by the possible cooling effect of particulate air pollution, which makes the clouds brighter and allows them to live longer, thereby reflecting more solar radiation and energy back to space. This cooling effect counters part of the warming due to the manmade emissions of greenhouse gasses such as C02 and methane, but to a poorly known extent. This uncertainty did not change substantially within the succession of 5 reports of the Intergovernmental Panel on Climate Change (IPCC) during the recent decades. The fundamental cause for this stagnation in our inability to use satellites to globally quantify the aerosol effect on clouds and, consequently, the Earth energy budget, stems from the fact that cloud properties are determined primarily by the rising air that cools aloft and condenses the excess moisture into cloud drops. The aerosol particles are the sites on which the cloud drops form, thus clouds in polluted air are composed of larger numbers of smaller drops, which are slower to coalesce into raindrops and result in longer living and brighter clouds that reflect more solar energy back to space. An emerging new capability to measure both updraft speeds and aerosols that can nucleate cloud drops can provide a clear vision to the future, which hopefully will lead to informed decision making. Here we show new ways to perform these critical satellite measurements that were considered impossible until now. This is done in part by novel use of existing satellites, and by development of a new satellite mission, in cooperation with NASA. The new mission is designed to measure cloud vertical motions by mapping the time evolution of the topography of cloud tops by photogrammetric methods that will be applied to multi-angle overlapping high resolution satellite images. Early results show the feasibility of measuring both updrafts and CCN. This represents the beginning of a revolution in the way that we will use satellites for weather and climate applications. This will improve predictions at all scales, from predicting weather at a scale of several hours to predicting possible climate changes at scales of decades and beyond.