In November Sage gave two seminars at the Churches Together in Oxfordshire Assembly “God's World? Christian Choices for the Future of the Earth”. The keynote speaker was the well-known writer and broadcaster Elaine Storkey, and she emphasised that the problem of global climate change needs tackling with great urgency. We felt that the time was right for a special edition of Sage Words on the topic, and approached two scientists (who also happen to be Christians) for contributions.

Sage had a busy autumn, with highlights being the Boundary Brook conservation work party, the Green Fair, and a wonderful New Year's Day walk in bright winter sunshine on the Ridgeway. The walk passed through the picturesque village of Lockinge, where we made a brief stop at All Saints Church (pictured). The day was rounded off with home-made curry at Martin and Margot Hodson's house in Grove.

One of the most frightening statistics I know of is the famous graph showing the increasing concentration of carbon dioxide in the atmosphere over the last century. It is already about 30% higher than it was before the Industrial Revolution and is projected to double in the next 30 years or so, an increase that is totally attributable to human activity such as the burning of coal, oil and gas. Most emissions come from the rich countries of the west; in the UK, Dr. Ian James

each household contributes some 9 tonnes of carbon to the atmosphere each year.

The likely effects of this increase are fiercely debated. Various lobby groups work hard to promote their vested interests, and the unavoidable uncertainties in any science are often exploited for very unscientific ends. At its simplest, doubling of carbon dioxide levels would lead to a “greenhouse” warming of the Earth of some 2 - 5 degrees C, although changing cloudiness, vegetation and competing polluting effects make the calculation more difficult and less certain. But there is accumulating evidence that there will be general temperature rises and changes of rainfall patterns, with some regions affected less, others much more than this average. Already we are probably seeing the first signs of these changes, with record breaking global mean temperatures in the last few years, the world-wide retreat of glaciers and an increase of the violence of extreme weather events.

What is the Christian to make of all this? One extreme view is that man-made climate change is irrelevant to the Church's business of saving souls. Another is to say that the Bible gives humankind dominion over nature; so if it suits us to destroy the environment, that is fine. The trouble with such positions is that they are based on a very narrow understanding of God. The first simply considers God as Redeemer of souls, the second simply as the omnipotent Creator delegating some of His power to people.

Christians understand God as Trinity, and that as stewards of creation, we are all called to seek to follow those same Trinitarian roles. God is Creator: He made the world and its finely balanced systems, and gave us responsibility for it. But God the Spirit is also the Sustainer, the One who holds together the world. We, as Children of God, need to find our own sustaining roles. Finally, God reveals himself in Jesus as the self-giving redeemer, suffering for the least of His creation. We too have to be ready to give ourselves for the rest of the creation.

Abuse of the environment amounts to abuse of our grandchildren. It is slowly being recognised by the Churches, not as an issue for cranks, but as central to a Gospel that has integrity. The rich west pleasing itself and failing to control consumption and pollution raises profound issues of justice for the majority of people who are not rich. We need to insist that our Churches take these matters seriously.

You only have to think of the different types of plants and animals associated with the different parts of the world to see that ecology is closely linked to climate. Rainforests are only found in places which are warm and wet, polar bears only live in very cold regions. It is therefore to be expected that if the climate of the British Isles changes there will be knock-on effects our wildlife.

The clearest and most straightforward change in climate predicted for Britain is a rise in temperature. We would therefore expect that species would be able to spread further north and to higher altitudes than they presently reach. This might present problems for those species of the highest altitudes and latitudes for which suitable climates may no longer be found in Britain. It is also possible that species previously not able to survive in Britain might be able to gain a toe-hold in the south and may eventually spread through the country. This could have both good and bad aspects to it. We might find that some of the very rare butterfly species in the south of England may increase and other interesting species, which are only occasionally seen here, may become resident. However it is also possible that some less benign non-native species may establish and displace long-standing British species. We only have to think of plants, like rhododendron and Japanese knotweed, that have been introduced and taken over areas, to see the sort of problems this might pose. It is worth noting that most species will be able to survive a few degrees warming, but they may not be able to compete successfully against species better adapted to the new conditions. We may have to manage nature reserves to prevent a few dominant species taking over - as is already done in some habitats such as chalk grasslands.

One aspect which introduces complexity is the different rates at which different organisms are likely to be able to migrate. Trees can only change their distribution very slowly - they don't move and take many years to grow up from seed. In contrast many animal species, move readily (especially those that fly) and breed quickly, allowing them to rapidly establish populations in new areas if conditions are suitable. This may mean that species will find themselves co-existing with different ones than at present. The implications for feeding and pollination, to name but two types of interactions between species, are still largely unknown.

Changes in temperature are not the only changes we may see in climate in years to come. There are predictions of more extreme weather and changes in rainfall patterns. In the south east it is possible that we will see both more summer droughts and winter floods as variability in rainfall increases and proportionally more falls in winter. These changes may have more impact than rising temperatures. There are, for example, concerns that beach trees may not survive extreme or prolonged droughts.