ALM UNDP

Summary:

This document aims to summarize and clarify the current understanding of the science of climate change for non-specialist readers. The document is structured around seven questions.

1 What is climate change?
Climate is a statistical description of weather conditions and their variations, including both averages and extremes. Climate change is a change in the average pattern of weather over a long period of time. Greenhouse gases play an important role in determining climate and causing climate change.

2 How has Earth’s climate changed in the distant past?
Global climate has varied enormously through Earth’s history. Evidence from the past shows that global climate can be sensitive to small influences. Past records also show that climates can shift abruptly.

3 How has climate changed during the recent past?
Global average temperature has increased over the past century. Evidence for this comes from instrumental temperature records in the air and the ocean. Temperature observations are not the only evidence of recent climate change: other sources include trends in sea levels, glaciers, ice caps and atmospheric water vapour that are consistent with global warming. Australia’s climate has changed along with global climate.

4 Are human activities causing climate change?
Human activities are increasing greenhouse gas levels in the atmosphere. It is very likely that most of the recent observed global warming is caused by this increase in greenhouse gases.

5 How do we expect climate to evolve in the future?
Climate models and studies of past climates indicate that global warming and associated changes will continue if greenhouse gas levels keep rising as they are now. It is very likely there will be significant warming through the 21st century and beyond. Reduction of greenhouse gas emissions could significantly reduce long-term warming.

6 What are the consequences of climate change?
Climate change will have significant impacts on our society and environment, both directly and by altering the impacts of other stresses.

7 How do we deal with the uncertainty in the science?
Although climate forecasts are uncertain and will remain so, the broad conclusions of climate change science as outlined above are based on many lines of evidence which together give a high degree of confidence. Partly because of scientific uncertainty but also because many aspects of human life are involved, decisions about action on climate change will need to involve extensive consideration of issues beyond science, including ethics, economics and risk management.

Image(s):