How to calculate & test for trend in time series

Question

I have yearly rainfall projections from five climate models for the period of 2010 through 2099.

This is a sample of my data:

df=structure(list(Year = c(2010, 2011, 2012, 2013, 2014, 2015, 2016, 
2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025, 2026, 2027, 
2028, 2029, 2030, 2031, 2032, 2033, 2034, 2035, 2036, 2037, 2038, 
2039, 2040, 2041, 2042, 2043, 2044, 2045, 2046, 2047, 2048, 2049, 
2050, 2051, 2052, 2053, 2054, 2055, 2056, 2057, 2058, 2059, 2060, 
2061, 2062, 2063, 2064, 2065, 2066, 2067, 2068, 2069, 2070, 2071, 
2072, 2073, 2074, 2075, 2076, 2077, 2078, 2079, 2080, 2081, 2082, 
2083, 2084, 2085, 2086, 2087, 2088, 2089, 2090, 2091, 2092, 2093, 
2094, 2095, 2096, 2097, 2098, 2099), CanESM2 = c(1163.46560706632, 
1045.27764563553, 1192.99035592859, 1039.18159594737, 1069.85056057463, 
1109.61718257189, 1080.22225446686, 996.465673784495, 1330.31482267773, 
1135.09951956191, 1036.5620174695, 1171.19645849667, 1230.07980354375, 
1224.51936031341, 1059.0667847652, 1119.61709915399, 1093.01684435802, 
1123.72623649933, 1088.75970830321, 1096.55713940808, 1136.73460669118, 
1225.56589926383, 1230.47636335948, 971.878201373981, 1077.94938659653, 
1067.66509425384, 1278.93601510725, 1132.26048108291, 1172.28768446317, 
1152.31800688181, 1226.66419877102, 1284.17386265492, 1065.46324990181, 
1126.16088253523, 1199.68965697911, 1048.76918572934, 1067.22448843151, 
1233.49853962937, 1125.31148343304, 1110.58047100806, 1096.19567721952, 
1277.141766876, 1024.98721582214, 1065.74405206603, 1067.80045192583, 
1115.30598493354, 1189.9948818424, 1437.13931627192, 1157.00834795935, 
976.858312813719, 1116.52499339511, 1111.09759483922, 1199.08438212517, 
1071.78135303469, 1007.25547265899, 1071.39018135202, 1089.81301384961, 
1312.96135982164, 1119.14850815955, 1128.62351901672, 1085.83469993455, 
1490.14291868226, 1082.82332451136, 1094.93028550704, 1138.81957874767, 
1097.4652709511, 1106.83810592802, 1229.91613882742, 1133.7894640904, 
1138.07334287779, 1281.84520786833, 1044.82250530464, 1187.35200775616, 
1156.74028624375, 1128.97358661251, 1168.80857077186, 1029.65489771463, 
1024.77267482949, 1085.6743046951, 1400.35428529776, 1165.82818082067, 
1117.43356446918, 1158.87599998443, 1188.6860869167, 985.854151901199, 
1147.12318390124, 1077.81579069868, 1154.53800683884, 1129.23840124991, 
1230.68311935564), `GFDL-ESM2M` = c(1110.40656291483, 1165.52810385097, 
986.538514416152, 1095.38727970136, 908.291964523058, 1015.48130275974, 
910.223751648018, 1037.17545203031, 1064.46407778575, 821.925055711163, 
1096.30232777925, 1145.56041166767, 994.615426183943, 1017.5660122588, 
1019.44059497268, 1074.6107636677, 1199.64822769138, 965.649952638057, 
947.58734190787, 946.097731390942, 1001.45702762066, 1115.81807500611, 
1037.58905387885, 917.925884051693, 974.408569840561, 1065.98187555499, 
988.032759990321, 1156.4922081412, 1053.23214676772, 868.078070630601, 
1117.82655721168, 1129.78430893212, 1078.10041660786, 792.460976651464, 
913.253156177221, 919.321633035608, 1040.56072059552, 1090.87082960431, 
1071.27625924979, 1033.46091240528, 883.895086023128, 939.489773000334, 
1102.2485093512, 779.851230298964, 1100.51135836672, 966.685826958901, 
961.744760284696, 989.753864405085, 826.629851232945, 909.284738712619, 
873.476834043498, 940.715939174158, 1005.83652099677, 1146.69688740834, 
978.082249009606, 1075.71089568088, 1101.2751541009, 962.851445193924, 
1024.69987402044, 1114.93474064477, 1024.47604232346, 1056.49825285734, 
975.492763800606, 1101.02607222684, 920.749421732859, 903.596908739447, 
912.489759611543, 987.64092666866, 808.10762021923, 973.408506903507, 
969.489829593018, 968.373783576046, 993.01049783438, 1080.98673871791, 
869.923091297771, 934.285784415424, 956.3081757549, 1013.38311159891, 
856.448744053944, 874.516625599295, 1061.51117387629, 1128.54448558007, 
1009.21257737855, 1017.16456465614, 833.802010570892, 927.740880449226, 
1001.38592283682, 952.145679780795, 996.893937239244, 931.957115223409
), inmcm4 = c(997.516654764994, 1145.13308691203, 959.542879520275, 
903.786765066992, 937.432661124838, 1007.46247945661, 1013.04583737278, 
1061.26827856464, 1056.61600975265, 892.433893874083, 1061.97862849247, 
978.554696188197, 939.55857188082, 996.416292720483, 1079.06762584418, 
1068.98156370385, 822.342905469512, 1019.26614712021, 1116.36245976214, 
1008.22817419423, 902.855504214986, 1087.38893040866, 885.956566984022, 
1016.16044809847, 1230.18564397572, 870.800309733513, 1037.21587559441, 
861.236791929213, 948.771432189766, 871.382698104435, 1089.3915218932, 
1054.49129365067, 941.903074357385, 973.558427724714, 938.638805666033, 
1006.66304703962, 863.28436030157, 806.021669160746, 869.369012721652, 
934.149986789314, 974.449974533922, 953.915114968656, 998.865234642777, 
949.027492106268, 967.701742440291, 952.306409621697, 959.027780253679, 
1033.69516116182, 992.987130941704, 1132.85542518598, 857.240436050392, 
1125.7240784834, 905.912164925948, 791.911242057151, 950.50688942409, 
684.62210670821, 928.505401464914, 898.455471168554, 881.937660493059, 
1043.17046368419, 990.173635925243, 872.642891720416, 968.112830276678, 
1156.70704372798, 954.681404468287, 1208.90589934053, 717.191066272881, 
985.50086154963, 1019.84388106248, 836.40573448035, 923.512492484388, 
942.453644704655, 1297.40333367214, 993.491117038875, 1035.26544859565, 
1056.57888641097, 968.592730428887, 887.591583109264, 1109.2935814163, 
923.189139410888, 972.33707020049, 1071.81484320842, 921.974872423456, 
956.677679924482, 886.258785523372, 903.500244794601, 1006.38055244068, 
914.283438551077, 779.704380831126, 1121.49522817412), 
`MRI-CGCM3` = c(848.301135629757, 
1065.98505740902, 888.813467571221, 1070.05226905271, 929.86581326247, 
949.338629810498, 1055.34828003874, 950.605580125944, 1025.98651471033, 
1062.58098758771, 1129.04220061327, 1113.69640112993, 983.264122816401, 
909.350171139101, 1049.76982306699, 991.477943714084, 1050.37713605355, 
957.954418661432, 1198.88425343781, 1019.03177011263, 892.820372968912, 
1117.83057226823, 1172.12350726162, 1045.54420748303, 1021.44374290702, 
1226.69766824788, 1076.26278716493, 892.835182446986, 1081.36552627508, 
1119.61825607435, 1101.7977981361, 1166.29589473449, 1114.24627378901, 
1111.95127710174, 1188.29593429323, 1005.43226899398, 1062.11294060983, 
1177.29197380333, 1233.89949211259, 949.362448506262, 1080.82477119637, 
848.404135782853, 1173.85210197539, 983.618625752799, 1023.98178052282, 
1174.67507789645, 1061.16686611069, 1145.73728230606, 1109.37233672472, 
1131.39932373277, 1192.52567101682, 1035.72075610234, 1170.69030772479, 
1402.30470791808, 828.360972784472, 1119.41148932651, 1418.65415788168, 
1111.1623167992, 1031.72445008109, 1133.74439397242, 1256.44423788796, 
1205.53255936418, 1246.028794886, 1353.06641467104, 1203.75084317503, 
1260.7607967303, 1133.17128359068, 1128.75225848513, 1248.50107501562, 
1125.34125579299, 1107.47674713103, 1286.39203071485, 1134.21641721783, 
1368.91059626765, 1249.62807137382, 900.188446846731, 1215.72863596362, 
1217.36216136844, 1239.46334238843, 1225.6431042983, 1293.28424474932, 
1316.91205393836, 1344.5824880094, 1431.35684547467, 1228.35587386956, 
1063.69382941901, 1366.01835107431, 1178.54993691379, 1425.59197731446, 
1439.18433794687), `NorESM1-M` = c(1104.36330130108, 1143.59864836685, 
1156.96992286211, 1225.47647032022, 1051.47222270552, 1225.96709059087, 
1169.02846946487, 1008.33133254077, 1041.4377020821, 1094.28488840048, 
1055.7942901173, 1182.85110699334, 1074.64700888046, 1220.40875347693, 
974.413995298429, 1082.02850933558, 1149.38849910412, 1177.55048525853, 
1159.36173358997, 1159.47946095381, 1013.84251995501, 1039.38081678502, 
1175.99482174589, 1075.9123379481, 1124.78923639009, 1072.4595220739, 
1059.99103769952, 1147.12456096131, 1054.66087104772, 1176.13768054148, 
1051.63089069775, 1124.1299767682, 958.783755377516, 1117.04595412512, 
1187.68311854194, 922.314885386565, 1118.97706673769, 1089.94177070272, 
1104.64546357211, 1129.91397601017, 1076.23273471979, 1117.36435679852, 
950.901478997885, 1171.61731400339, 1161.05025755828, 1122.1168542936, 
1132.68254406784, 1116.39483899695, 1052.38202713855, 1136.25445489531, 
1212.37181415053, 1113.58170133876, 988.657267351285, 1077.72113312282, 
1132.82563231238, 1060.24278563685, 1054.61879253374, 1138.19823195196, 
1086.79680899531, 1089.53650740066, 1101.56581663204, 1163.2291892284, 
1139.8293826996, 1125.56954148811, 1024.34059527431, 1152.0981675668, 
1064.32755358318, 1009.13933210229, 1210.55906508268, 1136.30532890842, 
1167.56870811327, 1163.3444730351, 1030.3320225021, 1334.11561872902, 
1186.00627022209, 1208.89776922561, 1172.03331588195, 1118.47337542874, 
1087.92709804022, 942.085245232004, 1159.78077235011, 1112.90807832063, 
1105.76965865985, 1104.31469614124, 1231.97413518222, 1228.57728152883, 
1208.44334175124, 1120.57185259478, 1014.7309899663, 1144.9384886849
)), .Names = c("Year", "CanESM2", "GFDL-ESM2M", "inmcm4", "MRI-CGCM3", 
"NorESM1-M"), row.names = c(NA, -90L), class = "data.frame")

Based on visual analysis, I suspect that there is a increasing precip trend in all models. But I need some kind of metric that can confirm an quantify this trend.

• For each model in this dataset, how can I calculate the rainfall trends for every year and for decades (2010-2019, 2020-2029 and so on)?
• Is it a simple linear regression of year against precip sufficient to show the trend?