Abstract. The present paper summarizes fungal spore emission fluxes in different biomes. A literature study has been conducted and emission fluxes have been calculated based on 35 fungal spore concentration datasets. Biome area data has been derived from the World Resource Institute. Several assumptions and simplifications needed to be adopted while aggregating the data: results from different measurement methods have been treated equally, while diurnal and seasonal cycles have been neglected. Moreover flux data were aggregated to very coarse biome areas due to scarcity of data. Results show number fluxes per square meter and second of 194 for tropical and subtropical forests, 203 for all other forests, 1203 for shrub, 2509 for crop, 8 for tundra, and 165 for grassland. No data were found for land ice. The annual mean global fluxes amount to 1.69 × 10 −11 kg m −2 s −1 as the best estimates, and 9.01 × 10 −12 kg m −2 s −1 and 3.28 × 10 −11 kg m −2 s −1 as the low and high estimate, respectively.

We consider decadal scale trends of annual mean all‐sky surface solar radiation (SSR) that occur solely because of internal variability of the climate system. We give statistical estimates of their magnitude and probability of occurrence. The estimates are based on 43 preindustrial control (piControl) experiments of the Coupled Model Intercomparison Project phase 5 (CMIP5). Trends are found to depend strongly on geographical region and on whether they are quantified in absolute units or relative to the long‐term mean SSR. We find it to be sufficient to provide one map for absolute and one for relative trends, as approximate analytical relations are shown to hold between trends of different length and likelihood and the standard deviation of the underlying SSR time series. We estimate that a positive trend over 30 years and with 25% chance of occurrence (75th percentile of all possible trends) has a magnitude between 0.15 and 1.7 W/m2/decade or 0.11 and 1.4% of long‐term mean SSR per decade, depending on geographical location. Comparison with present‐day observations and intermodel spread suggests an average uncertainty of these estimates of about 30%. Intermodel spread suggests that regional uncertainties can be up to about 3 times larger or smaller. We give examples of how these results may be used to obtain statistical estimates of how (un)likely it is that observed SSR trends or part thereof are due to internal variability alone.

Anthropogenic aerosols reduce incoming surface solar radiation (SSR), but the magnitude of this effect for reducing sea surface temperatures (SST) is still debated. Using simulations from the global climate model ECHAM5 with the Hamburg Aerosol Module and prescribed SSTs, we quantify anthropogenic aerosol dimming over sea surfaces by comparing ensembles, which only differ in anthropogenic aerosol emissions. We isolate the anthropogenic aerosol effect on SSR with sufficiently large ensemble sizes to provide statistically significant results. The following simulation results are obtained: Dimming plumes extend from their source regions with clear seasonality. The latter is predominantly shaped by atmospheric circulation, while interdecadal changes follow the gradual increase in anthropogenic aerosol emissions. Comparing the 1990s with the 1870s, on average, 9.4% (clear-sky SSR) or 15.4% (all-sky SSR) of the entire ocean surface was affected by anthropogenic aerosol dimming larger than −4 Wm −2 (decadal mean). Comparing the same time periods, global average anthropogenic dimming over oceans is −2.3 Wm −2 and −3.4 Wm −2 for clear-sky and all-sky SSR, respectively. Surface dimming is hemispherically asymmetrical with stronger Northern Hemispheric dimming by 2.3 Wm −2 and 4.5 Wm −2 for clear-sky and all-sky SSR, respectively. Zonal average clear-sky dimming reaches its maximum (−5.5 Wm −2 ) near the equator. All-sky dimming peaks at 40 ∘ N (−8 Wm −2 ) and is regionally larger than clear-sky dimming. Regionally, surface dimming can reach values up to 9.5 Wm −2 (clear-sky) and 25 Wm −2 (all-sky). Results are a contribution toward better quantifying spatially heterogeneous and time-dependent anthropogenic dimming effects on SSTs.

Clean air policies can have significant impacts on climate in remote regions. Previous modeling studies have shown that the temperature response to European sulfate aerosol reductions is largest in the Arctic. Here we investigate the atmospheric and ocean roles in driving this enhanced Arctic warming using a set of fully coupled and slab-ocean simulations (specified ocean heat convergence fluxes) with the Norwegian Earth system model (NorESM), under scenarios with high and low European aerosol emissions relative to year 2000. We show that atmospheric processes drive most of the Arctic response. The ocean pathway plays a secondary role inducing small temperature changes mostly in the opposite direction of the atmospheric response. Important modulators of the temperature response patterns are changes in sea ice extent and subsequent turbulent heat flux exchange, suggesting that a proper representation of Arctic sea ice and turbulent changes is key to predicting the Arctic response to midlatitude aerosol forcing.Plain Language Summary Aerosols are liquid or solid particles suspended in air, which may have adverse air quality and health impacts. Sulfate aerosols also have a cooling influence on climate and can mask some of the greenhouse gas-induced global warming. While aerosol emissions are variable in space and time, their impacts are not limited to where they are emitted. In fact, studies using global climate models have shown that changing sulfur dioxide emissions in Europe can have significant impacts on Arctic climate. Here we investigate the roles of changes in atmospheric and ocean heat transport in driving these changes in the Arctic by conducting a series of climate model simulations with specified anthropogenic sulfur dioxide emissions and different ocean heat transport fluxes. We find that changes through the atmosphere play a primary role in affecting the Arctic climate. These changes are modulated by changes in sea ice extent and the energy exchange between ocean and atmosphere in the sub-Arctic. Aerosol-driven changes in ocean heat transport play a smaller, secondary role in the Arctic and tend to reduce the impacts. Our results show that the proper representation of Arctic sea ice is crucial for accurately modeling the Arctic response to changes in midlatitude aerosol forcing.