Climate FAQs

Weather and climate refer to different aspects of meteorology.

Weather is the brief, rapidly changing condition of the atmosphere at a particular place and time, usually changing from hour-to-hour and town-to-town, influenced by the movement of air masses.

Climate, on the other hand, is more stable, describing the average weather over at least 30 years.
For example, winter is colder than summer, and Melbourne is colder than Darwin. Just as a cricketer’s batting average is rarely hit during a particular match, the (average) climate conditions do not always exist in a particular year.

Climate variability and climate change are different facets of climate.

Climate variability refers to the year-to-year variations around the average conditions, meaning that consecutive summers will not all be the same, with some cooler and some warmer than the long-term average.
Climate change refers to any long-term trends or shifts in climate over many decades, around which climate variability is evident year to year.

Hence, a single warmer or cooler decade on its own is not sufficient evidence to assert climate change is or isn’t occurring, but statistically significant changes in average conditions over many decades do provide evidence of a changing climate.
Australians have learned to live with climate variability such as droughts and flooding rains, or hot and cold years, but our coping capacity is limited.

We are vulnerable to extreme events, as shown by the economic, social and environmental costs of recent fires, floods, heatwaves, droughts and cyclones.

Human-induced climate change, represents a raft of new challenges for this generation and those to come, through increases in extreme weather events and other changes, such as sea-level rise and ocean acidification.

Climate change will be superimposed on natural climate variability, leading to a change in the frequency, intensity and duration of extreme events. Climate risk profiles will be altered and adaptation will be necessary to manage these new risks. Adaptation includes new management practices, engineering solutions, improved technologies and behavioural change.

Read more about our climate change research.

There is a great deal of evidence that the Earth’s climate has warmed over the past century. Both natural and human influences have affected climate over this time, but it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

The evidence that climate has changed over the past century includes temperature observations over land and sea, as well as measurements of rainfall, sea levels, and ocean acidity and salinity. Over time, these measurements give us a picture of how climate has changed, both in Australia and globally.

The heat content of the world’s oceans has increased during recent decades and accounts for more than 90 per cent of the total heat accumulated by the land, air and ocean since the 1970s.

On a global scale, the ocean warming is largest near the surface, and the upper 75 m warmed by between 0.09°C and 0.13°C per decade over the period 1971–2010.

In Australia, surface temperatures on the land have been recorded at many sites since the mid to late 19th century.

By 1910, Australia had a reliable network of thermometers and the data they produced have been extensively analysed by the Bureau of Meteorology and scientists at CSIRO, Australian universities and international research institutions.

This reveals that since 1910, Australia’s annual-average daily maximum temperatures have increased by 0.75°C and the overnight minima by more than 1.1°C.

Since the 1950s, each decade has been warmer than the one before. We’ve also experienced an increase in record hot days and a decrease in record cold days across the country. Some years have been relatively cool due to effects such as La Niña, but overall the trend is clear and distinct: Australia has become warmer.

There has been a general trend towards increased spring and summer monsoonal rainfall across Australia’s north during recent decades, and decreased late autumn and winter rainfall across southern Australia. Sea-surface temperatures around Australia have increased faster than the global average.

Sea levels can change for a variety of reasons over a range of different time scales. At the daily timescale, sea levels might change as a result of tides, wave activity or storm surges, as well as events such as earthquakes and tsunamis.

There are some changes that occur as a result of seasonal changes, such as warming in summer and cooling in winter in both hemispheres, and some are annual changes associated with natural climate variability, such as El Niño and La Niña events.

Of greatest interest to researchers studying climate change are the sea-level changes occurring over multiple decades.

Average global sea levels have been rising consistently since 1880 (the earliest available robust estimates) largely in response to increasing concentrations of greenhouse gases in the atmosphere and the consequent changes in the global climate.

There are two main processes behind long-term sea-level rises, which are a direct result of a warming climate. Firstly, as the ocean has warmed the total volume of the ocean has increased through thermal expansion of water. Secondly, water has been added to the oceans as a result of melting glaciers and ice sheets.

Sea levels began to rise in the 19th century and the rate of sea-level rise since the mid-19th century has been larger than the average rate during the previous two millennia. Global-average sea levels are currently (between 1993 and 2010) rising at around 3.2mm per year, faster than during the 20th century as a whole.

Rates of sea-level rise are not uniform around the globe and vary from year to year.

Since 1993, the rates of sea-level rise to the north and northwest of Australia have been 7 to 11 mm per year, two to three times the global average, and rates of sea-level rise on the central east and southern coasts of the continent are mostly similar to the global average.

These variations are at least in part a result of natural variability of the climate system.

Read more information about sea level change.

Ocean heat

One of the best indicators of changes in the climate system is the amount of heat stored in the oceans.

The heat content of the world’s oceans has increased during recent decades and accounts for more than 90 per cent of the total heat accumulated by the land, air and ocean since the 1970s.

This warming increases the volume of ocean waters and is a major contribution to sea-level rise. Ocean warming is continuing, especially in the top several hundred metres of the ocean.

Sea surface temperatures in the Australian region were very warm during 2010 and 2011, with temperatures in 2010 being the warmest on record. Sea surface temperatures averaged over the decades since 1900 have increased for every decade.

Sea surface temperature datasets are separate to land temperature datasets, but both land and ocean surface temperatures have shown very similar warming trends over the last century, confirming that temperatures are rising.

For more information see – State of the Climate 2012

Ocean Acidification

As well as storing heat, the world’s oceans absorb a vast amount of carbon dioxide (CO₂). The ocean currently absorbs about a quarter of the CO₂ emitted into the atmosphere each year.

As atmospheric CO₂ concentration increases, the amount of CO₂ absorbed and stored in the ocean also increases. Ocean acidification is a direct result of CO₂ absorption. The CO₂ taken up by the ocean reacts in the seawater to increase the oceans acidity levels, measured in terms of pH.

Since the beginning of the industrial era, the absorption of the increasing amounts of atmospheric CO₂ has decreased ocean surface water pH by 0.1, or a 26 per cent increase in the hydrogen ion concentration, and changes are expected to decrease pH by a further 0.06-0.32 by 2100, depending on the level of CO₂ emissions in future.

Ocean acidification has been shown in laboratory and field studies to reduce the growth of carbonate shells and skeletal material of many key organisms, including reef-building corals. Other effects include causing a change in the development of early life stages of some species, although the response to ocean acidification varies considerably between species.

As these organisms span the entire marine food chain, ocean acidification could have far reaching implications for the health and productivity of the world’s oceans.

For more information see – State of the Climate 2012

Greenhouse gases in the atmosphere insulate our planet’s surface against the chill of space, something known as the greenhouse effect.

The main greenhouse gases influenced directly and emitted by human activities are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and synthetic gases such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs).

Water vapour and ozone are also significant greenhouse gases, whose concentrations in the atmosphere are controlled mainly by the Earth’s temperature and the emission of ozone producing chemicals, such as reactive hydrocarbons, and ozone destroying chemicals like CFCs.

Global CO₂, CH₄, and N₂O concentrations have risen rapidly during the past two centuries, which has enhanced the greenhouse effect and contributed to global warming. The amount of these long-lived greenhouse gases in the atmosphere reached a new high in 2013. The concentration of CO₂ in the atmosphere in 2011 was 391 parts per million (ppm) – much higher than the natural range of 170 to 300 ppm during the past 800 000 years.

The relative contributions to the enhanced greenhouse effect from pre-industrial times to 2013, due to the long-lived greenhouse gases, are: CO₂ (64 per cent), CH₄ (18 per cent), synthetics (12 per cent) and N₂O (6 per cent).

Global CO₂ emissions are mostly from fossil fuels (more than 85 per cent), land use change, mainly associated with tropical deforestation (less than 10 per cent), and cement production and other industrial processes (about 4 per cent). Energy generation continues to climb and is dominated by fossil fuels – suggesting emissions will grow for some time yet.

For more information on changes to the atmosphere see – State of the Climate 2012 – Understanding Greenhouse Gases

With greenhouse gas emissions continuing to increase, we expect the warming trend of the past century to accelerate throughout this century. We also expect changes to rainfall patterns and to the frequency of extreme weather events like cyclones and droughts.

The Earth’s future climate will depend on whether the world manages to slow or even reduce greenhouse gas emissions. Since greenhouse gases have a long lifetime in the atmosphere, any change in emissions will have a delayed effect on atmospheric concentrations, so these concentrations are expected to increase, leading to further warming and climate change for many decades.

Different emissions scenarios have been developed, based on different assumptions about future demographic change, economic development and technological advances. The concentrations paths are similar up to about 2030, and then diverge markedly.

Average temperatures across Australia are projected to rise by 0.4 to 1.8°C by 2030, compared with the climate of 1990. By 2070, warming is projected to be 1.0 to 2.5°C for a low emissions scenario, and 2.2 to 5.0°C for a high emissions scenario. Australians will experience this warming through an increase in the number of hot days and warm nights and a decrease in cool days and cold nights.

Climate models show that there may be less rainfall in southern areas of Australia during winter and in southern and eastern areas during spring. Wet years are likely to become less frequent and dry years and droughts more frequent.

Climate models suggest that rainfall near the equator will increase globally, but it’s not clear how rainfall may change in northern Australia.

Australia will also experience climate-related changes to extreme weather events. In most areas of the country, intense rainfall events will become more extreme.

Fire-weather risk is also likely to increase and fire seasons will be longer. And although it is likely that there will be fewer tropical cyclones in the Australian region, the proportion of intense cyclones may increase.

A changing climate leads to changes in the frequency, intensity, spatial extent, and duration of extreme weather and climate events. These include extreme temperatures, heatwaves, drought, flooding, bushfires, tropical cyclones, and storm surges.

The natural climate variability that underlies all extreme weather events is now influenced and altered by the effect of human-induced warming of the climate system.

Future climate change impacts will be experienced mostly through extreme events rather than gradual changes in mean temperature or rainfall.

Heatwaves, floods, fires and southern Australian droughts are expected to become more intense and more frequent. Frosts, snow and cyclones are expected to occur less often.

Extreme events and natural disasters place a huge burden on individuals, communities, industry and the government and have an enormous impact on Australia’s economy, social fabric and environment.

Better preparing for extreme events through planning, management, engineering and awareness has proved to be effective in reducing their cost.

Over recent decades, we have developed approaches to better prepare for and manage the impacts of extreme events: e.g. new cyclone building codes, improved warning systems, greater coordination between emergency management responses, and improved pest and disease surveillance.

However, in the last four years more than 550 people lost their lives in natural disasters and the costs of repairing public and private infrastructure, insurance claims and lost productivity has run to tens of billions of dollars. Sudden and unexpected disease or pest outbreaks can also heavily impact human health, the economy and the environment: agriculture, tourism and water supplies all depend on the integrity of our biosecurity systems.

CSIRO climate researchers use climate simulations to project future climate decades in advance. These models are based on the Laws of Physics and are run on supercomputers.

They use mathematical representations to simulate the complex interactions of the Earth’s climate system, including atmospheric, oceanic, hydrological and terrestrial processes and atmospheric chemistry.

The models are validated by simulating climate in previous decades and then comparing the results of the model with recorded measurements of temperature, rainfall and other climatic variables.

There are over 40 climate models around the world. Some simulate the past climate better than others, especially at the sub-continental scale, so it is important to derive regional projections from models that perform well.

One such model is ACCESS, the Australian Community Climate and Earth System Simulator. ACCESS produces the Bureau of Meteorology’s Australian weather forecasts, which you see on the evening news.

This is one of the models that CSIRO researchers are using to project climate in the coming century, building on more than 20 years of research into developing climate projections for Australia.

Australia is expected to experience an increase in extremely high temperatures, extreme fire weather, extreme rainfall events, tropical cyclone intensity, extreme sea levels, and droughts in southern areas.

A decrease in the frequency of extremely cold temperatures is expected, along with fewer tropical cyclones. These changes will pose significant challenges for disaster risk management, water and food security, ecosystems, forestry, buildings, transport, energy, health and tourism.

For example, many animal and plant species may decline or become extinct, water resources are expected to decline in southern Australia, agricultural zones are likely to shift, coastal erosion and inundation is expected to occur more often, energy demand is likely to increase, snow cover will decline and heat-related deaths may rise.

Find out more about Climate change impacts.

Climate mitigation is refers to the reduction of greenhouse gases to limit the amount of climate change that may occur. Climate adaptation equips society to cope with the changes that are already happening or that are unavoidable in the future.

Adaptation and mitigation are closely linked: the less we mitigate, the more we will be forced to adapt to inevitable changes in the climate, and the bigger the adaptations will have to be.

Conversely, success in mitigation through early and deep cuts to greenhouse gas emissions will necessitate fewer, less extreme adaptations in the long term.

Climate mitigation

Research and development is vital for the continuous creation, improvement and adoption of new technologies to help mitigate climate change. For example, research into renewable energy is an essential part of Australia’s energy mix and will play an increasingly important role as we move to reduce greenhouse gas emissions and secure future energy supply.

Wind, solar, biomass and geothermal energy provide sustainable options to deliver our energy and transport needs.

Scientific research can also:

• improve the reliability, efficiency and affordability of renewable energy technologies enabling them to become a major energy source in Australia;
• improve building design and energy efficiency to reduce our energy consumption and carbon dioxide emissions from commercial buildings and homes;
• develop alternative routes to fuel production and transportation power that could lead the way to a sustainable future for road, rail, air and water transport, and;
• develop new technologies to improve efficiency in the resources sector and maximise the benefits of Australia’s abundant coal, uranium, gas and oil resources.

For more information see Mitigation strategies for energy and transport.

Climate adaptation

Some climate change and consequent impacts are unavoidable due to the greenhouse gases that are already in the atmosphere and as future emissions increase. To limit the social, economic, and environmental impacts of these changes, we need to adapt.
Scientific research can lead to the development of solutions to help us adapt to climate challenges.

Three areas are critical to successful adaptation to climate change – decision making and how to go about it, the development of specific solutions (technical and other) to climate challenges, and the analysis of barriers to the adoption of systems and technologies that will help us adapt.

Australia is leading the way in the coordinated approach to these areas of adaptation research.

For more information see Adaptation reducing risk gaining opportunity.
Learn more about CSIRO’s Climate Adaptation Flagship

A distinction needs to be made between science that is robust and science that is relatively uncertain. All conclusions should be based on peer-reviewed literature, and, where possible, levels of confidence should be provided.

In climate change science, the robust findings include:

• clear evidence for global warming and sea level rise over the past century
• changes observed in many physical and biological systems are consistent with warming
  due to the uptake of anthropogenic CO₂ since 1750, ocean acidity has increased
• most of the global average warming over the past 50 years is very likely due to anthropogenic greenhouse gas increases
  global greenhouse gas emissions will continue to grow over the next few decades, leading to further climate change
• due to the time scales associated with climate processes and feedbacks, anthropogenic warming and sea level rise would continue for centuries even if greenhouse gas emissions were to be reduced sufficiently for atmospheric concentrations to stabilise
  increased frequencies and intensities of some extreme weather events are very likely
• systems and sectors at greatest risk are ecosystems, low-lying coasts, water resources in some regions, tropical agriculture, and health in areas with low adaptive capacity
• the regions at greatest risk are the Arctic, Africa, small islands and Asian and African mega-deltas. Within other regions (even regions with high incomes) some people, areas and activities can be particularly at risk
• some adaptation is underway, but more extensive adaptation is required to reduce vulnerability to climate change
• unmitigated climate change would, in the long term, be likely to exceed the capacity of natural, managed and human systems to adapt
• many impacts can be reduced, delayed or avoided by mitigation (net emission reductions). Mitigation efforts and investments over the next two to three decades will have a large impact on opportunities to achieve lower greenhouse gas stabilisation levels.

Some of the key uncertainties include:

• observed climate data coverage remains limited in some regions
• analysing and monitoring changes in extreme events is more difficult than for climatic averages because longer data sets with finer spatial and temporal resolutions are required
• effects of climate changes on human and some natural systems are difficult to detect due to adaptation and non-climatic influences
• difficulties remain in reliably attributing observed temperature changes to natural or human causes at smaller than continental scales
• models differ in their estimates of the strength of different feedbacks in the climate system, particularly cloud feedbacks, oceanic heat uptake and carbon cycle feedbacks
• confidence in projections is higher for some variables (e.g. temperature) than for others (e.g. precipitation), and it is higher for larger spatial scales and longer averaging periods
• direct and indirect aerosol impacts on the magnitude of the temperature response, on clouds and on precipitation remain uncertain
  future changes in the Greenland and Antarctic ice sheet mass are a major source of uncertainty that could increase sea level rise projections

• impact assessment is hampered by uncertainties surrounding regional projections of climate change, particularly precipitation
• understanding of low-probability/high-impact events and the cumulative impacts of sequences of smaller events is generally limited
• barriers, limits and costs of adaptation are not fully understood
• estimates of mitigation costs and potentials depend on uncertain assumptions about future socio-economic growth, technological change and consumption patterns.

Hence, the science isn’t settled but there are enough robust findings to provide a basis for action through mitigation of greenhouse gases as well as adaptation to reduce our vulnerability to climate change impacts.
Further research is needed to reduce the uncertainties and quantify confidence levels.

There is a lot of information on climate change science available in the media and on the web, but how can you ensure what you are reading is independent and not influenced by personal, social or political agendas?

The peer-review process provides a mechanism to quality control scientific discourse and therefore peer-reviewed papers provide a reliable and quality-assured source of information on climate change science.

Science relies on the continued questioning and challenging of ideas. When a new hypothesis or finding is published in a scientific journal, other scientists will take it seriously because it has been through the peer-review process.

Once an article is published in a peer-reviewed journal, its ideas can be challenged or supported by other scientists with peer-reviewed articles of their own.

For scientific journals, the process starts with the submission of a manuscript. The editorial staff refer the manuscript to at least two impartial reviewers who are qualified to judge the competence, significance and originality of the research.

The reviewers’ comments are passed to the authors of the manuscript with a covering note from the editor, indicating whether changes need to be made before the manuscript is acceptable for publication.

The final decision about whether the manuscript should be published lies with the editor.

Major reports are normally peer-reviewed. For example, the Intergovernmental Panel on Climate Change (IPCC) assesses the peer-reviewed literature on climate change every five to six years.

The reports are subject to an intense peer-review process involving hundreds of scientific experts and government reviewers. This unprecedented level of peer and government review makes this compendium of climate change science one of the most scrutinised documents in the history of science.

See Intergovernmental Panel on Climate Change [external link].

Drawing from peer-reviewed information, CSIRO and the Bureau of Meteorology release a regular a snapshot of the state of the climate; a summary of the latest climate science, adaptation and mitigation peer-reviewed research is available in CSIRO’s free climate book; and CSIRO’s website has a large amount of general information about climate change.

You may also like to look at a number of other non-CSIRO sites, including:

• Australian Bureau of Meteorology [external link]
• Skeptical science [external link]
• Real Climate [external link]
• UK Met office [external link]