1. Leavesembedded in the form of fossils are an excellent way to predict the historicclimates by assessing the identifying the nearest current relative. For exampleby examining the fossils of Nyssa and Taxodium from the Miocene era (5 millionto 23 million years ago) of the Rhine area of Germany, it can be inferred thatthe climate of Germany was different than it is today. This is because themodern relatives of these fossils are found in warm and humid environmentscontrary to the cold temperatures that prevail in Germany today. USpalaeontologist Jack Wolfe studied the physical appearance of leaves andcompared them with the climatic condition around the world. Wolfe illustratedthat the shape of the leave margin and its edge varies with mean annualtemperature such that in higher temperatures, most plants have full smoothmargins of the leaves whereas toothed edges are mostly found in colderenvironments.
Moreover leaf size also varies with temperature variations acrossenvironment because leaf size is directly proportional to water loss. 2. Theprotective surface called cuticle and pores called stomata on the surface ofthe leaves can also infer about the environmental conditions of the obtainedfossils. For examples plant leaves with thick cuticles and less stomata on theleaves reveal that they were growing in a hot and dry climate and thus lessstomata to avoid excessive water loss.3. Holocenesummer temperature reconstructions from northern Europe based on suggest anonset of peak summer warmth around 9,000 years ago. In a study, pollen-basedtemperature reconstructions about the summer temperatures from northern Europerevealed that summer warmth reached its peak some 9,000 years ago.
The evidenceis obtained from sedimentary pollen records and are mostly affected by changesin the proportions of tree taxa. When the tree pollen taxa of the plants suchas spruce (Picea abies) in north-eastern European Russia, pine (Pinus sylvestris)in northern Fennoscandia and Alnus incana, Alnus glutinosa, Ulmus glabra,Corylus avellana, Tilia cordata and Quercus robur rose, the rises intemperature occurred simultaneously. This study has also shown that aquaticplant macrofossil records can provide additional information about theearly-Holocene temperature evolution in northernmost Europe. Moreover it canfurther suggest the development of post-glacial climatic condition usingmulti-proxy data.