Protecting forests from agricultural expansion and wildfires while the world population is growing and the climate is warming remains one of the biggest challenges humanity currently faces. While global modelling and regional observation based studies have found significant effects from deforestation on precipitation, leading mostly to drying precipitation trends and shorting rainy seasons, this study represents the first global estimate of first order deforestation effects on precipitation. Using a recently developed precipitationshed database and actual deforestation data, a new measure is developed to quantify potential deforestation impact per grid cell which in turn is related to annual precipitation trends as well as seasonal differences in tropical regions. In seven regions analysed, a majority of subregions suggested a relationship between deforestation impact and a relative drying precipitation trend in the 2001-2018 study period compared to the long term average. While these results provide further evidence of deforestation contributing to a downwind drying precipitation trend across different continents and climate regions, five other regions studied showed no significant relation or suggest relative wetting related to deforestation impact. One of this regions is the South America Tropical (SAT) region, the region most well-known for its widespread and intense Amazonian deforestation. The two regions downwind of the SAT region however are highly impacted by SAT deforestation and experience most relative drying in the areas impacted most impacted by deforestation, suggesting strong teleconnecting effects. In the seasonal analysis, only two out of four tropical regions studied show more subregions linking deforestation impact to relative drying in the first wet month compared to the wettest month. While these results provide new insights into the global influence deforestation can have on moisture availability, more research needs to be done into the indirect and feedback effects related to deforestation. Additionally, a more robust way of including other factors influencing precipitation trends like large scale oscillations could further enhance the understanding of this important issue.

The knowledge deficit model assumes that people make more informed decisions when they are presented with more information. This model is often used in communication strategies while it has received quite some critique from science communicators and is not well supported by social science theories. One of these critiques comes from the observed Dunning-Kruger effect, where individuals unskilled in a certain area do not possess the skills to realize their incompetence. This effect has not been researched extensively yet in relation to climate change science communication and is the topic of this paper. By means of an online questionnaire (316 respondents), respondent’s knowledge and estimated knowledge on climate change is tested. The Dunning-Kruger effect has been detected for this group and suggests a critical re-evaluation of the knowledge deficit model, however additional research is necessary. An initial analysis into the influence of factors like age, gender and highest completed education level on actual and estimated scores and the discrepancy between these is also done to provide leads for further research.

Clouds and aerosols continue to contribute to the largest uncertainty to estimates and interpretations of the Earth's changing energy budget. By comparing relative humidity (RH) and attenuated backscatter ratio (ATB) data and deriving scattering hygroscopic enhancement factors at the Cabauw Experimental Site for Atmospheric Physics Research (CESAR), an attempt is made to better understand the process of aerosol hygroscopic growth. This is done by ground based ceilometer, hygrometer and SMPS technology gathering data during the ACCEPT campaign in 2014, resulting in a high temporal resolution, continuous measurements and the possibility to compare the data with ancillary information measured on the same location. Some aerosol number concentration (ANC) data is also taken into account as indication of the influence of ANC on ATB. For the three studied time intervals with a large variation (>30%) in RH, a convincing relation between RH and ATB is found, which can be linked to the Köhler curve when a direct relation between aerosol size and ATB is assumed. For these three time intervals, scattering hygroscopic enhancement factors are derived with similar γ values as reported in previous studies. Further research is required to analyze the correlation between RH and ATB more and rule out other influences on ATB.