Large differences in regional precipitation change between a first and second 2 K of global warming

For adaptation and mitigation planning, stakeholders need reliable information about regional precipitation changes under different emissions scenarios and for different time periods. A significant amount of current planning effort assumes that each K of global warming produces roughly the same regional climate change. Here using 25 climate models, we compare precipitation responses with three 2 K intervals of global ensemble mean warming: a fast and a slower route to a first 2 K above pre-industrial levels, and the end-of-century difference between high-emission and mitigation scenarios. We show that, although the two routes to a first 2 K give very similar precipitation changes, a second 2 K produces quite a different response. In particular, the balance of physical mechanisms responsible for climate model uncertainty is different for a first and a second 2 K of warming. The results are consistent with a significant influence from nonlinear physical mechanisms, but aerosol and land-use effects may be important regionally

Historical total ozone radiative forcing derived from CMIP6 simulations

Radiative forcing (RF) time series for total ozone from 1850 up to the present day are calculated based on historical simulations of ozone from 10 climate models contributing to the Coupled Model Intercomparison Project Phase 6 (CMIP6). In addition, RF is calculated for ozone fields prepared as an input for CMIP6 models without chemistry schemes and from a chemical transport model simulation. A radiative kernel for ozone is constructed and used to derive the RF. The ozone RF in 2010 (2005–2014) relative to 1850 is 0.35 W m−2 [0.08–0.61] (5–95% uncertainty range) based on models with both tropospheric and stratospheric chemistry. One of these models has a negative present-day total ozone RF. Excluding this model, the present-day ozone RF increases to 0.39 W m−2 [0.27–0.51] (5–95% uncertainty range). The rest of the models have RF close to or stronger than the RF time series assessed by the Intergovernmental Panel on Climate Change in the fifth assessment report with the primary driver likely being the new precursor emissions used in CMIP6. The rapid adjustments beyond stratospheric temperature are estimated to be weak and thus the RF is a good measure of effective radiative forcing

Calculating the O3 Instantaneous Longwave Radiative Impact from Satellite Observations

Ozone is a key atmospheric substance for both chemistry and climate. Being a secondary species, its concentration is controlled by a number of different factors, such as precursors’ emission, sunlight and oxidizing agents. Its impact on atmospheric chemistry and radiative balance differs with altitude: in the lower troposphere ozone acts as a toxic pollutant, in the upper troposphere as a greenhouse gas (GHG) and finally in the stratosphere as a protection against harmful ultraviolet (UV) radiation. Ozone is in general a radiatively active gas for both solar (shortwave, SW) and terrestrial (longwave, LW) radiation [14], therefore it’s very important to acquire and understand its radiative impact for climate related studies.info:eu-repo/semantics/publishe

Is there a stratospheric radiative feedback in global warming simulations?

The radiative impacts of the stratosphere in global warming simulations are investigated using abrupt CO2 quadrupling experiments of the Coupled Model Inter-comparison Project phase 5 (CMIP5), with a focus on stratospheric temperature and water vapor. It is found that the stratospheric temperature change has a robust bullhorn-like zonal-mean pattern due to a strengthening of the stratospheric overturning circulation. This temperature change modifies the zonal mean top-of-the-atmosphere energy balance, but the compensation of the regional effects leads to an insignificant global-mean radiative feedback (-0.02 +/- 0.04 W m(-2) K-1). The stratospheric water vapor concentration generally increases, which leads to a weak positive global-mean radiative feedback (0.02 +/- 0.01 W m(-2) K-1). The stratospheric moistening is related to mixing of elevated upper-tropospheric humidity, and, to a lesser extent, to change in tropical tropopause temperature. Our results indicate that the strength of the stratospheric water vapor feedback is noticeably larger in high-top models than in low-top ones. The results here indicate that although its radiative impact as a forcing adjustment is significant, the stratosphere makes a minor contribution to the overall climate feedback in CMIP5 models.National Science and Engineering Research Council of Canada [RGPIN418305-13]; Fonds de recherche du Quebec-Nature et technologies; National Natural Science Foundation of China [41025018]; National Basic Research Program of China (973 Program) [2010CB428606]; Korea Ministry of EnvironmentSCI(E)[email protected]