title: Citizen science shows systematic changes in the temperature difference between air and inland waters with global warming.
abstract: Citizen science projects have a long history in ecological studies. The research usefulness of such projects is dependent on applying simple and standardized methods. Here, we conducted a citizen science project that involved more than 3500 Swedish high school students to examine the temperature difference between surface water and the overlying air (Tw-Ta) as a proxy for sensible heat flux (QH). If QHis directed upward, corresponding to positive Tw-Ta, it can enhance CO2and CH4emissions from inland waters, thereby contributing to increased greenhouse gas concentrations in the atmosphere. The students found mostly negative Tw-Taacross small ponds, lakes, streams/rivers and the sea shore (i.e. downward QH), with Tw-Tabecoming increasingly negative with increasing Ta. Further examination of Tw-Tausing high-frequency temperature data from inland waters across the globe confirmed that Tw-Tais linearly related to Ta. Using the longest available high-frequency temperature time series from Lake Erken, Sweden, we found a rapid increase in the occasions of negative Tw-Tawith increasing annual mean Tasince 1989. From these results, we can expect that ongoing and projected global warming will result in increasingly negative Tw-Ta, thereby reducing CO2and CH4transfer velocities from inland waters into the atmosphere.
authors.affiliation: Department of Ecology and Genetics/Limnology, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden.
authors.forename: Gesa A
authors.initials: GA
authors.lastname: Weyhenmeyer
authors.affiliation: Science and Technology Branch, Environment and Climate Change Canada, 4905 Dufferin Str. Toronto, Ontario, M3H5T4, Canada.
authors.forename: Murray
authors.initials: M
authors.lastname: Mackay
authors.affiliation: Rubenstein Ecosystem Science Laboratory, University of Vermont, 3 College Street, Burlington, Vermont 05401, USA.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Stockwell
authors.affiliation: Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland.|Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussels, Pleinlaan 2, 1050 Brussels, Belgium.|Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, 3001 Leuven, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Thiery
authors.affiliation: Department Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Alte Fischerhuette 2, 16775 Stechlin, Germany.|Institute for Biochemistry and Biology, Potsdam University, Maulbeerallee 2, 14469 Potsdam, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
authors.affiliation: Remote Sensing Department, National Institute of Space Research (INPE), São José dos Campos, São Paulo, Brazil.
authors.forename: Pétala B
authors.initials: PB
authors.lastname: Augusto-Silva
authors.affiliation: School of Environment and Sustainability and Global Institute for Water Security, University of Saskatchewan, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Baulch
authors.affiliation: Marine Institute, Furnce, Newport, Co. Mayo, Ireland.
authors.forename: Elvira
authors.initials: E
authors.lastname: de Eyto
authors.affiliation: Biology Centre CAS, Institute of Hydrobiology, Na Sádkách 7, 370 05 České Budějovice, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Hejzlar
authors.affiliation: Centre for Limnology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 61117 Rannu, Estonia.
authors.forename: Külli
authors.initials: K
authors.lastname: Kangur
authors.affiliation: Dept. of Ecohydrology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
authors.forename: Georgiy
authors.initials: G
authors.lastname: Kirillin
authors.affiliation: Department of Ecology and Genetics/Limnology, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden.
authors.forename: Don C
authors.initials: DC
authors.lastname: Pierson
authors.affiliation: Dorset Environmental Science Centre, Ontario Ministry of the Environment and Climate Change, P0A 1E0, Dorset, ON, Canada.|Department of Biology, Queen's University, K7L 3N6, Kingston, Canada.
authors.forename: James A
authors.initials: JA
authors.lastname: Rusak
authors.affiliation: Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Sadro
authors.affiliation: Department of Meteorology, University of Reading, Reading, UK.
authors.forename: R Iestyn
authors.initials: RI
authors.lastname: Woolway