Figure 1 (Ortiz-Llorente & Alvarez-Cobelas)

Figure 1 (Ortiz-Llorente & Alvarez-Cobelas)

Figure 2 (Ortiz-Llorente &Alvarez-Cobelas)

Figure 3 (Ortiz-Llorente & Alvarez-Cobelas)

Figure 4 (Ortiz-Llorente & Alvarez-Cobelas)

Figure 5 (Ortiz-Llorente & Alvarez-Cobelas)

Figure legend

Figure 1. Methane emissions worldwide in different latitudes and climate types according to Köppen´s Climate Classification (a) Annual emissions vs latitudes, (b) Peak emission vs latitudes and (c) Peak emissions and climate. 0-10º, n = 13 and 102, respectively for (a) and (b), 10-20º, n = 6 and 33, respectively; 20-30º, n = 5 and 20, respectively; 30-40º, n = 38 and 47, respectively; 40-50º, n =66 and 105, respectively; 50-60º, n = 50 and 87, respectively; 60-70º, n = 69 and 119, respectively; 70-80º, n = 6 . Cold continental (CC) sites are 115, equatorial sites (E) 114, Mediterranean sites (M)-7, oceanic sites (O)-15, subarctic (S)- 77, steppe sites (ST)-37, tropical sites (T)-71, and warm temperate sites (WT)-84. Boxes include 25-75% of overall data, open squares are median values and whiskers comprise the whole range of data.

Figure 2.

(a) Peak emissions in different marine ecosystems incoastal shelf (CS, n = 26), deep sea (DS, n = 20), estuary (E, n = 18) and upwelling (U, n = 5) ecosystems. Outliers in estuaries (n = 2) and coastal shelves (n = 1) have not been represented; see Appendix 1 (Supplementary Material) for their values.

(b) Peak emissions in different wetland types: coastal wetlands (CW, n = 9), forested wetlands (FW, n = 43), marshes (M, n = 102), and peatlands (P, n = 179).

(c) Peak emission in wetlands with different plant dominance. Bryophyte- (B, n = 75), big helophyte- (BH, n = 60), hydrophyte- (H, n = 14), small helophyte- (SH, n = 128) and tree-dominated (T, n = 53) wetlands are shown.

(d) Peak emission in lakes as related with eutrophication and thermal regime (separate by a dashed line. Oligotrophic (O, n = 98), eutrophic (E, n = 44), non-stratifying lakes (NS, n = 132) and stratifying lakes (S, n =10).Plots as in Figure 1.

Figure 3. Seasonality of methane emission in (a) ecosystem types and (b) in either ice-free- or winter-frozen wetlands, as shown by the Kavvas and Delleur (1975) approach (seetext).Estuary (E),lake (L), river (R), and wetland (W).No seasonal data are available for ocean sites. All time series for each ecosystem-year have been scaled by expressing emission as the percent differencefrom the annual mean. All ecosystems are either located in the Northern Hemisphere or their time course of emissions has been changed accordingly to enable seasonal comparisons. The horizontal line represents the mean.

Figure 4. Spatial variability of peak emission in lakes (L, n = 9), wetlands (W, n = 20) and oceans (O, n = 19). No data are available for streams. The few data available for estuaries are included within the ocean type. Plots as in Figure 1.

Figure 5.

(a) Annual emission worldwide plotted against methane peak emission. Annual emission = 4.78 * peak emission – 7.33. n= 44. r2 =0.93, p< 0.05.

(b)Peak emission plotted against annual emission < 50 g CH4 m-2 yr-1 (close squares), Annual emission =2.97 * peak emission + 0.10. n = 31. r2 = 0.92, p < 0.05 and against annual emission above 50 g CH4 m-2 yr -1 (open square), Annual emission = 4.98 * peak emission - 13.96. n = 13. r2 = 0.89, p < 0.05.