The important factors for the agrarian output in Bulgaria are only thermal and water probability. From the two factors, the component related to soil moisture is more limited. As well water and temperature probabilities in the agrarian output are estimated through stuns of temperatures and rainfalls or by derivative indicators (most frequently named as coefficients or indices). The heat conditions and the heat resources are specified by the continuousness of the vegetative period. Duration of vegetative season is limited for each type of plant, between the spring and autumn steady pass of air temperature across the biological minimum. For the agricultural crops in Bulgaria, the three biological minimums in 5 degrees C are taken for wheat and barley, oat, pea, and lentil; in 10 degrees C for sunflower, corn, haricot, and soybean; and in 15 degrees C for the cotton, vegetables, and other spring cultures. The cold and warm period duration are mutually related characteristics. The first period defines the number of days with the snowfall and days with the snow cover that are the basis in the formation of soil moisture reserves after the spring snow melt. Definition of the regions with temperature stress conditions during vegetative season is one of the most important parameters of agroclimatic conditions. The values indicating for the limitations are one or more periods from at least 10 consecutive days with maximal air temperature over 35 degrees C. More from the agricultures, character for the moderate continental climatic zone are developed normally under temperatures 25-28 degrees C. Temperatures over 28 degrees C are ballast slowing the growth and destroying plants due to the heat tension. The component, limiting in greatest degree growth, development and formation of yields from the agricultural crops are the conditions of moisturizing, present trough atmospheric and soil moisture. The most apparent indicator is the year sum of the rains or their sum by the periods with the average daily temperatures of over 5 and 10 degrees C. Cross correlation matrix between the meteorological elements from which evapotranspiration depends - temperature, relative air humidity, wind speed, and the vapor pressure deficit - is present. The data about the limitations, emergent from the soil moisture lack, to the base of the existing agrometeorological data are present. Values of the relation between real and potential evapotranspiration were calculated for potential vegetative period which is divided up to the two subperiods, March to June, the period of formation outputs from wintering cultures, and July to August, the period of formation outputs from the spring cultures. In the 1980s and 1990s, science led debates "for" and "against" climate change. During this time they published dozens of monographs and among them are Sir John I loughton's Global Warming: The Complete Briefing and John T. Hardy's Climate Change: Causes, Effects, and Solutions. The first of them was translated into Bulgarian by the author of this paper and published in 1996 by the academic publishing house of Prof. M. Drinov. Of course, they published numerous other studies and hundreds of articles, reports, and messages (Olmstead, Rhode, Creating abundance: biological innovation and American Agricultural Development. Cambridge University Press, 2008; Croitoru et al, Glob Planet Change 102:10-19, 2013; Rosenzweig, Hillel, Climate change and the global harvest: potential impacts of the greenhouse effect on agriculture. Oxford University Press, 1998; Georgieva, Kazandjiev, Sci Pares Ser A Agron LVI:459-467, 2013; Georgieva et al, Europa XXI 29:43-58, 2015; Kazandjiev, Peev, Prerequisites for disaster by natural weather phenomena and processes, reports first scientific-practical conference on Emergency Management and Civil Protection, Sofia, Bulgarian Academy of Sciences 10.11.2005, pp 186-193 (in Bulgarian), 2005d; Kazandjiev, Agroclimatic resources and definition of less favored areas at the beginning of XXI century in Bulgaria, Conference "Global Environmental Change - Challenges to Science and Society in Southwestern Europe." CD version, 2008a; Rattan et al, Climate change and global food security, CRC, 2005; Roumenina et al, Int J Remote Sens 34(8):2888-2904, 2013; Pritchard, Amthor, Crops and enviromnental changes. Haworth Press (US), 2005; Simeonov, Georgiev, Atmos Res 57:187-199, 2001; Sivakumar et al, Natural disasters and extreme events in agriculture. Springer, 367 pp, 2005; Slavov, Relationship between climate change and desertification. Problems of land degradation and combating desertification. UN str.42-48 (in Bulgarian), 1998; Slavov, Alexandrov Drought Netw News 5(2):12-15, 1993). Today science has a lot of evidence in favor of climate change. But now science nationally and globally faces new questions: How far will climate change reach? How will the various sectors of the economy adapt to change? How will agriculture in particular adapt to climate change? What must the action plan 2030-2050 contain? The purpose of this paper is to plot a strategy for the adaptation of agriculture in Bulgaria to climatic change. This will establish the vulnerability of the main types of crops to climate change and will define criteria for extreme meteorological phenomena and processes of agro-meteorological point of view. The team will assess the risk of dangerous agriculture phenomena and combinations thereof, through probabilistic and statistical research. Also we will present indices that can be used as indicators for proof of climate change. As a result, they will identify adaptation measures by regions and types of cultures and develop a strategy for adaptation of Bulgarian agriculture to changing environmental conditions.
