The radiative forcing resulting from condensation clouds behind aircraft (“contrails”) has been estimated to have an effect on the same order of magnitude as all accumulated aviation-attributable CO₂. However, contrail impacts are highly uncertain, with estimates of total contrail-driven forcing made in the past five years varying by a factor of 4. Two of the key driving uncertainties are the crystal shape and size, which describe the cloud optical properties. Here we combine data from high-fidelity scattering simulations of single crystals with in situ measurement of bulk contrail ice properties to bound the range of realistic optical properties for contrail ice. Accounting for the full range of measured contrail microphysical evolution pathways, and for a given estimate of contrail coverage, we find that the global net radiative forcing due to contrails in 2015 is between 8.6 and 10.7 mW/m². Relative to the midpoint, this uncertainty range is less than one-quarter of that recently reported in the literature. This reduction in uncertainty is primarily due to the elimination of spheres as a plausible long-term shape for contrail ice, leaving questions of contrail coverage and optical depth as the primary causes of contrail forcing uncertainty.

中文翻译：

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减少因冰晶特性不确定性而导致的对流辐射强迫的不确定性。

据估计，由飞机后方的凝结云（“轨迹”）产生的辐射强迫与所有累积的航空归因的CO ₂具有相同数量级的影响。但是，轨迹转换的影响是高度不确定的，在过去五年中对轨迹转换驱动的强迫进行的估计相差4倍。两个关键的不确定因素是晶体的形状和大小，它们描述了云的光学特性。在这里，我们将单晶的高保真散射模拟数据与原位相结合测量凝结尾冰的性质以限制凝结尾冰的实际光学性质范围。考虑到所测量的所有轨迹变化的轨迹，以及轨迹轨迹覆盖的给定估计值，我们发现，轨迹轨迹在2015年的全球净辐射强迫在8.6和10.7 mW / m ^2之间。相对于中点，该不确定性范围不到文献中最近报道的范围的四分之一。不确定性的降低主要是由于消除了球体，这是凝结尾冰的合理的长期形状，留下了凝结尾迹覆盖范围和光学深度问题，这是造成凝结强迫不确定性的主要原因。