Here the most frequently asked questions on climate change are presented and answered.

What is climate and how is it different from weather?

Climate is the statistical behaviour of weather over periods of time. Weather is the state of the atmosphere at a specific place and time in regards to moisture, temperature, wind, pressure, etc. Climate describes the average conditions in a region over a number of years, while weather describes conditions at the local scale during a short period in time. The main difference between climate and weather is time.

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What is climate change?

Climate change refers to a change in the statistical distribution over decades or longer. The term itself includes changes in climate due to natural earth conditions and human-induced activities. The United Nations Framework Convention on Climate Change defines climate change as "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is, in addition to natural climate variability, observed over comparable time periods." 

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What are the linkages / interdependencies between climate change, climate variability and global warming?

Climate variability encompasses the natural variation in different weather phenomena that occur from day to day and season to season. This has always occurred and will continue even as the climate is changing as result of the additional changes from human-induced climate change. Global warming refers to human-induced climate change while reinforcing the rising temperature. 

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How do we know that the climate is changing and what the climate will be in the future? 

To know how the climate is changing and what the future climate could be like, the climate models are used to produce climate scenarios.

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What are climate models?

Climate models are used to calculate the future climate and to produce climate scenarios. These models are three-dimensional representations of the atmosphere, land area, ocean, lakes and ice. 

In global climate models the atmosphere is divided into a grid horizontally along the earth’s surface and vertically into the air. At every point in the grid the development of different meteorological, hydrological and climatological parameters in time are calculated. For global models the size of each square in the grid is 100—300 km, while in regional models a smaller area of the earth is modeled e.g. over Europe with grid squares of 25—50 km. Over a smaller area, a denser grid can be created without demanding so much extra computer power so greater detail can be achieved. What happens outside the calculated area in a regional climate model is controlled by the results of the global climate model so that consideration is also taken to changes outside of the regional model area. 

At the local level, one would choose regionally downscaled climate information if it is available, as the detail in regional models is greater. If this is not available, even information from global climate models can give some indication of future climate, but in a coarser way. 

Figure 1. Typical resolutions over Europe in a regional (right) and global (left) climate model

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What are climate scenarios? 

Climate scenarios present information on how the climate could possibly develop during a determined period of time in the future. They are created by government authorities dealing with meteorology or climate issues and/or research institutes with the help of global climate models. The calculations are based on assumptions about future changes in the atmosphere. They include the relationships between physical processes in the entire atmosphere-land-water system, as well as emission scenarios, which are assumptions about future emissions of greenhouse gases. Results from these global models can be downscaled further with regional models to provide greater detail. 

The results, which are based on calculations with the climate models, are called climate scenarios. Climate scenarios are not weather forecasts. Weather forecasts give information about what is probably going to happen at the local scale during a short period in time. Climate scenarios represent the statistical behavior of weather, which we call climate, but they do not recreate the real weather at a specific place and time.

When comparing future climate to our current climate, reference periods are often used e.g. of 20 or 30 years. The results for the future are often compared with the average for this reference period. Normally the period 1961—1990 is used as standard reference.

As the information from climate scenarios are calculated in the form of a grid (gridded data), it is difficult to compare this information to current climate observations, which are taken at specific locations (point data). Observations describe the conditions at a specific point, while models describe conditions evenly distributed over the whole grid. One can look at the example of precipitation. If a large amount of rain falls over a very small area, it would be recorded at one measuring station. At other nearby places which might have only received small amounts of rain or no rain at all, the measurement stations will record much smaller amounts. If the same total amount of precipitation is created in the model for the grid in question it will be evenly spread over the grid. This would make it appear as if it has rained evenly over the entire the grid while in reality (compared to observational measurements) the rain was much more unevenly distributed.

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What are emission scenarios? 

Emission scenarios are assumptions about the future emissions of greenhouse gases, which are used in climate modelling. They are prepared by the United Nation’s climate panel, IPCC (Intergovernmental Panel on Climate Change). Emissions scenarios are based on assumptions about how the world will develop in the future including the economy, population growth, effects of globalization and changes to environmentally friendly technology. The amount of greenhouse gases that will be emitted over time depends on global development. A number of emissions scenarios are described in the IPCC report on emissions scenarios (IPCC, 2000).

The emissions of the different greenhouse gases can change in different ways between and within the different scenarios. This means that the scenario showing the largest change in temperature in 100 years might not necessarily be the one showing the largest change in 20 years. 

Figure 2. Emissions of CO2 according to different scenarios (IPCC, 2001a)

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How are climate scenarios prepared for specific areas? 

When climate scenarios are prepared for a specific area, the results are analyzed for all grids that cover the chosen district. For every point in time, an average value for all grids in the area is taken in order to produce a time series for the area. Often, information is presented in diagrams covering parameters such as temperature, precipitation, snow cover, wind, etc. calculated with running 10-year annual average values for the whole time series. This average helps to show a trend over time. Time series of higher resolution (e.g. daily, monthly and even annual) are often noisy and hard to interpret.

Maximum and minimum values are the highest respective lowest values in a particular point during the same time period. These values are useful to show the spread and variability of the data. We know the average, but at a specific time everything between the minimum and maximum may occur.

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There are sceptics who disagree with the climate change scenarios. How can I know whether climate change is really a problem?

The scientific research in the climate change field is constantly improving the models from which they get their results and the field of research is inherently a process in development. The developed takes place through discussion between scientists and disciplines. When reading critiques, it is important to keep in mind that climate science is extremely complex and models used in different scientific fields account for different parameters and different submodels in their modelling. Though it is acknowledged that the climate has always had large variations including ice ages, the IPCC has now, based on observations and relations to greenhouse gas emissions, declared that there is a clear relationship between human activities and temperature rise.

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What is “uncertain” about climate scenarios?

Climate scenarios depend on which emission scenarios and global and/or regional models are used in the calculations. This is especially true about the quantitative results (e.g. how much rain or how much temperature will increase). For example, comparative studies have shown that the global model ECHAM4 gives a temperature and precipitation change during winter in northern Europe that is larger than in many other climate models. This means that blindly accepting the results of one or two climate scenarios is risky as the results vary between models.

In addition there is natural variability in climate. It cannot be expected that the climate results from a model are in phase with the real climate. These results are averages over a certain period of time and may not reliably reflect the real climate variability. A high quality climate model however should calculate good average values and characteristic variability, e.g. the right number of cold and warm winters during a 30-year period (though not necessarily the actual winters). The cold and warm winters could nevertheless occur in another sequence than in the observed climate.

To look at results from several model simulations gives the opportunity to consider uncertainties and also to estimate which results are robust. Conflicting results might seem confusing, but one should make use of the extra information that they provide. If the models give different results, then the uncertainty of the results is high. If the models on the other hand give similar results, then the certainty of the results is high. Besides looking at several scenarios one by one, it is possible with statistical methods and specific analyses to combine several simulations and get a result that is better than any separate simulation. 

This means that the more climate scenarios which one has access to, the greater the opportunity to deem the certainty of the results. Unfortunately, information from several models is not always available. If using results from only one or a few climate scenarios, then more caution should be used in accepting the results.

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What are the main causes and drivers of climate change?

Climate is varying on several timescales, from hours to thousands of years. These cycles are determined by a number of factors. Astronomical factors, such as the distance between the earth and the sun and the shape of the earth’s orbit around the sun, steer the longest variations like ice age cycles (1000—100 000 years). At a relatively shorter time scale (10—100 years) climatic variations are determined by among others ocean circulations and variation in the sun’s radiation. Today, the most prominent factor driving climate change is greenhouse gases.

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What are greenhouse gases and what is their role?

The most common and effective greenhouse gases are water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs). Common to these gases is that they all absorb outgoing radiation from earth to space, contributing to the greenhouse effect. In short, the greenhouse effect is that some of the heat radiated from earth towards space is absorbed by the greenhouse gases in the atmosphere and reemitted towards the earth, thus increasing the temperature. Without the atmosphere, earth would be much colder than it is. If the amount of greenhouse gases in the atmosphere increases from e.g. human activities, more radiation is absorbed into the atmosphere, thus increasing the temperature further.

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How can we tell whether climate change is caused by man-made (anthropogenic) and not natural processes? And why is there some controversy over this?  

It is very unlikely that the 20th-century warming can be explained by natural causes. The rapid warming during the last 100 years is consistent with the scientific understanding of how the climate should respond to a rapid increase in greenhouse gases, like that which has occurred over the past century. Additionally, the warming is inconsistent with the scientific understanding of how the climate should respond to natural external factors, such as variability in solar output and volcanic activity.

Numerous experiments have been conducted using climate models to determine the likely causes of the 20th-century climate change. These experiments indicate that models cannot reproduce the rapid warming observed in recent decades when they only take into account variations in solar output and volcanic activity. The human influence on climate very likely dominates over all other causes of change in global average surface temperature during the past half century.

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What are the future impacts of climate change?

Scientific observations have shown that climate change has impacts on natural- and human systems both regionally and globally (IPCC, 2007a). The climate system and the lifetime of the GHG emissions result in some of the future climate change impacts to be unavoidable. Climate change and the many effects it entails are therefore an important research area for development of climate change mitigation and adaptation strategies.

Several methods are used and developed in order to obtain knowledge about climate change impacts, adaptation and vulnerability, to in turn to improve the basis for making decisions (IPCC, 2007a). Within the BalticClimate project a review of climate change impacts in the Baltic Sea Region was undertaken. The aim with this review was to provide a compilation of the currently available knowledge concerning climate change impact scenarios of relevance for the Baltic Sea Region. For further details click here.

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How will climate change affect me and my community/my area?

The scenarios of projected climate change differ from area to area. However, you might be able to get local, regional or national climate scenarios from national organisations, such as your national meteorological or hydrological institutes. 

The IPCC provides a general description of the anticipated effects on Europe, along with other regions, in their report: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Summary for Policymakers.

Also within the Baltic Sea Region future climate scenarios are available both on the transnational/supraregional scale as well as regional/local scale.

Although it is not possible to say what the impacts of such scenarios on a specific area might be and when they might happen without detailed studies, impact studies already done can provide you with an idea of potential changes your area might experience. However, the impacts that your area might experience from climate change, depends on a number of issues, including, how you are affected by changes in your environment (sensitivity) and what kind of capacity you have to adapt to those changes (adaptive capacity).

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What is vulnerability to climate variability and change?

There are three major approaches or mental models on vulnerability to climate change (Füssel and Klein, 2006). 

Risk hazard approach

The risk hazard approach, which is often used by spatial planners, engineers and the natural hazard community, frames vulnerability as the risk that a certain event will occur. Risk is thus defined as the product of probability and consequence (e.g. Brooks, 2003; Füssel and Klein, 2006). This approach mainly relates to sensitivity, that is how significantly climate change will impact society and nature. 

Social constructivist approach

The social constructivist approach has its origins in human geography and political economy (Adger, 1999). Here, vulnerability is seen as a condition of a household or a local community that is assumed before the real analysis starts. This condition is determined by socio-economic and political factors (Adger and Kelly, 1999) thus underlining the non-climatic drivers of change that affect social systems. 

Integrated approach

The third approach frames vulnerability as an integrated measure and is prominent in studies of global change. The IPCC in its third assessment report defined vulnerability in an integrated manner as:

the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change”, and it is seen as a function of “the character, magnitude, and rate of climate change and variation to which a system is exposed and the sensitivity and adaptive capacity of that system” (IPCC, 2001b).

Accordingly, vulnerability contains an external dimension, that is the exposure to environmental and economic change determined outside the local community, and an internal dimension capturing the sensitivity and adaptive capacity of the local community to these mainly externally determined stressors. It is not only the existence of adaptation measures that limits climate vulnerability, but also and more importantly, the capacity of social organisations — households, businesses, public agencies — to put these measures into practice. It is this implementation deficit that needs to be recognized, discussed and, hopefully, overcome.

According to IPCC definition the vulnerability is related to three inter-related elements: exposure, sensitivity, and adaptive capacity. Exposure and sensitivity are hard to separate in a system. Exposure represents what risks the local community is facing and how much a system is stressed, while sensitivity addresses how much these stressors actually modify or affect the studied system. Adaptive capacity depicts the ability of a system to adjust to climate change in order to moderate potential damages, take advantage of opportunities, or cope with the consequences (IPCC, 2001b). For more in-depth descriptions of these three elements, see here.

Figure 3. Vulnerability and its components (modified from Fig. 1 in Australian Greenhouse Office, 2005) (click to enlarge)                

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Is climate change all negative? Are there ways to benefit from it?  

Not all the impacts of climate change will be negative — it differs widely from region to region. In the Baltic Sea Region, for example, many see the overall increase in temperature which is projected by many scenarios, to bring a relative advantage to this area in terms of tourism.

Moreover, potential benefits can be best taken advantage of by those prepared in time for potential changes. An understanding of one’s local circumstances, along with the potential climate related stressors are the keys to mapping your own vulnerability to climate change and variability. Furthermore, developing an action plan for decreasing your vulnerability, as well as being aware of the opportunities that might come to exist is necessary to then take advantage of the opportunities. 

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Where can I find further information about climate change?

European Commission Climate Campaign 
Denmark - Climate Change Adaptation  
Estonia - Ministry of Environment - Climate portal
Finland -
Germany - Competence center on climate impacts and adaption KomPass
Germany - Federal Environment Agency's climate change info 
Germany - Federal Ministry for the Environment, Nature Conservation and Nuclear Safety - climate info
Latvian Academy of Sciences - Climate change and its impact
Latvian Center for Public Policy - Climate discussion page 
Latvian National Research programme - Climate change impact on water environment 
Lithuania - Ministry of Environment, climate change
Lithuanian Hydrometeorological Service
Norway - Climate adaptation Norway  
Russia -
Russia - Federal Service for Hydrometeorology and Environmental Monitoring
Sweden - Swedish Meteorological and Hydrological Institute  

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