Direct health effects of climate change
The climate is a significant, constantly varying factor in our living environment. Through changes taking place in the environment, climate change can have a direct or indirect effect on our health. These effects can be short-term and strong or occur continuously for long-term. Of the direct environmental factors affecting humans, solar radiation and temperature are focal. In addition, extreme weather conditions – storms, heavy rain and floods – have a direct impact on us.
Darker winters have an effect on our mental health
The weather influences the mood and health of humans. Approximately one per cent of Finns suffer from actual seasonal affective disorder (SAD) and every tenth person suffers from symptoms similar to SAD during the winter. During the darkest time of the year, lack of sunlight and snow can weaken sleep quality and have an effect on our alertness and eating habits. 
Although the climate warms on average, amount of sunlight is not increased. In fact, sunlight is projected to reduce and cloudy weather become more common with climate change, particularly in the winter. In addition, outdoor exercising possibilities are reduced if there is little snow. In the future, Southern and Western Finland will have more and more winters with little or no snow that, in part, deteriorates the possibilities to do winter sports. This may have detrimental health effects if the overall amount of exercise reduces. Moreover, craving for sugary foods related to seasonal affective disorder can increase the risk of becoming overweight.
In connection with health effects related to climate change, there is only little research regarding the connection of severe depression with prolonged rainy and cloudy weather. The connection of lack of snow and cloudy weather to our health is yet to be clarified. However, it has been proven that severe depression occurs most during the autumn and winter while the risk of suicides increases from November to March when there is little sunlight. The number of suicide cases is at its highest during spring which is believed to be caused by the rapidly increasing sunlight during the early spring. 
Health effects of temperature
To some extent, our bodies are adjusted to tolerate fluctuating temperatures. Limits to our adjustment are set by the local climate conditions along with the optimum status in which mortality caused by temperature is at its lowest. Temperature-dependent mortality risk can be described with a u-shaped graph in which the mortality risk increases if the temperature rises or drops markedly and cold or hot weather limit values are exceeded. In Finland, the mortality rate directly linked to temperature is at its lowest at approximately 14 ̊C. When the average daily temperature remains above 20 ̊C for 1–2 weeks, there is a clear increase in mortality .
In North Europe, the temperature threshold values are lower than in the south because people living in the north are more susceptible to heat rather than cold . Because the body has not had time to adjust to the high temperatures, heat waves occurring during the early summer are the most dangerous. Children, elderly people, athletes and people working outdoors are particularly vulnerable to extreme temperatures. Despite a good health status, active exercising or physical work outdoors increases the risk of health hazards. Since hot weather impedes working and concentrating, facilities without air-conditioning are particularly harmful for indoor workers. In addition, chronically ill patients are a part of the risk group because their weakened resistance makes them susceptible to high temperatures. Very high and low temperatures have also been proven to increase the risk of premature death for patients suffering from cardiovascular diseases, respiratory and nervous system diseases. In addition, ability to tolerate heat is weakened by pharmaceuticals having an impact on sweating and dehydration.
Climate change will increase hot days and heat waves in Finland
As the building stock quality has improved in Finland and elsewhere in Europe, the number of heat-related deaths has decreased over the last decades . Annually, less than 200 people die as a consequence of hot weather in Finland, while the cold season causes 2,000–3,000 premature deaths . Proving a death is directly caused by hot weather is difficult, as the mortality risk may also be affected by other environmental factors, human physiology and behaviour and weather is only one additional factor.
Climate change increases the intensity and duration of the heat waves. More than 30,000 premature deaths were reported as a consequence of heat waves during the summer of 2003 in Western Europe . In Finland, the heat wave in 1972 is estimated to have increased the number of deaths by 840 and the hot weather in 2003 by 250 cases. The effect people have on the climate is assessed to at least double the risk of heat waves like the one in 2003 occurring again.  There are time-related, regional and population-characteristic-related differences in the mortality rates caused by heat waves. Although, in many cases, mortality increases exponentially when the temperature rises, compared to single hot days, mortality is higher during extended periods of hot weather . In addition to the number of hot days, it is important to assess how many consecutive hot days occur during the longest hot weather period in the summer. This information is useful in measuring health services, for example.
Since the population in Finland is not as adjusted to high temperatures, health effects caused by hot weather can be expected at lower temperatures than in Central and Southern Europe. Increased number of hot days and prolonged heat waves will have the most detrimental effect on the inhabitants of the Metropolitan area in Finland. Compared to the surrounding countryside, in a closely built area, the temperatures during summer nights remain higher due to the so-called urban heat island phenomenon. During summer days, buildings, asphalt and stone surfaces in cities store heat more than unbuilt areas and release this heat during the night. Thus, the temperature in cities cools down slower than in the countryside. Moreover, air pollution and lack of vegetation intensify the adverse health effects in cities. During heat waves, disabled elderly people living alone are particularly at risk, since their possibilities to react to the elevation in the temperature are limited. Size of the risk is influenced by social contacts and financial position, thus low income or homeless people or people living far from services have a higher risk of dying from heat waves .
Not all changes related to climate have negative impacts on the health of Finns. Approximately 30 per cent of Finns suffer from a chronic disease that is sensitive to cold . For them, the warming climate will most likely decrease morbidity and mortality.
UV radiation harms the health of more and more Finns
As the ozone layer in the atmosphere thins, sun's UV radiation on the surface of the ground becomes stronger. Although chemicals destroying the ozone layer are estimated to reduce in the upcoming decades, the ozone layer recovers slowly. This is due to the fact that a warming climate lowers the temperatures in the middle atmosphere which might feed the ozone destroying processes. Since the annual variation is great both due to changes in the ozone amount and clouds, the measurement time series of UV radiation are not yet long enough to determine with certainty if radiation has increased. For example, during the summer of 2009 in Finland, UV radiation was clearly stronger than normal, but one year has no bearing on the long-term trend. Although this has not yet been proven with certainty, climate change may reduce cloudy weather during the summer to some extent.
Increased exposure to UV radiation has increased skin cancer and eye diseases among the population. In addition to a possible change in the radiation climate, increased exposure is caused by behavioural changes . Selection of clothing, travels to the south and the previously prevailed fashion of being tanned have probably had a greater impact on the overall dose of radiation than climate change.
Preparing for hot weather
Heath effects and mortality caused by high summer temperatures can be prevented by arranging air-conditioned facilities and adequate ventilation capacity to nursing homes and hospitals. With respect to elderly people living at home, attention should be paid to training home care workers and informing of the health effects of hot weather in media aimed at the elderly. During a heat wave, social networks and neighbours are important sources of help and can save the life of an elderly person living alone.  
Over the long term, the urban heat island phenomenon can be alleviated with community planning.Since green areas do not store as much heat as stone and asphalt surfaces, placing green areas and plantations among the buildings and streets cools down the microclimate. In addition, trees provide shade for citizens and reduce the cooling need of buildings with their shading. Placement of buildings, design and choice of materials can further influence how easily the temperature rises inside buildings during hot weather. Generalisation of apartment-specific air-conditioning and ventilation devices also helps adapt to the occasional periods of hot weather.   However, increased air-conditioning causes increased consumption of energy and if it is based on fossil fuel, this impedes mitigation of climate change.