Human contributions to climate change – how we know
Earth’s climate is changing. We are able to directly observe this as glaciers melt and disappear and Arctic sea ice declines. The Earth’s average temperature is steadily rising. Globally since 1880, 19 of the 20 warmest years have occurred since 2001. Aotearoa is following this trend. The country’s annual land-surface temperature has risen by an average of 1.1℃ since records began in 1909.
New Zealand’s annual temperature is rising
This graph shows the temperatures from decade to decade and year to year.
Graph by Ministry for the Environment, Stats NZ, and data providers and released under the CC BY-NC-ND 4.0.
The Intergovernmental Panel on Climate Change states that the current warming trend is extremely likely to be the result of human activity since the mid-20th century.
How do we know that climate change is the result of human activity? We know that the Earth’s climate has changed in the past. Change naturally happens – so why are humans responsible for this period of change? The simple answer is that we know, from various lines of evidence, that humans are the source for almost all of the extra greenhouse gases accumulating in the atmosphere.
Nature of science
Scientists collect data about current climate events through direct observation, such as daily weather measurements. They also collect data about past climate events through direct observation of greenhouse gases trapped in ice cores.
The role of research and data
Scientists have been interested in the relationship between carbon dioxide and atmospheric temperature for more than a century. The link between fossil fuel emissions and warming was first proposed in 1896. This interest was ignited when systematic atmospheric CO2 measurements from Mauna Loa, Hawaii, showed that CO2 levels were steadily rising. Other monitoring stations, including Baring Head in New Zealand, confirmed this trend. Measurements from sites around the globe show that rises in CO2 levels have accelerated in recent years.
How do we know the data is robust?
NIWA scientist Gregor Macara and MetService Meteorological Data Manager Kevin Alder explain how they collect standardised data, while Our atmosphere and climate 2020 authors Drew Bingham and Bonnie Farrant explain quality checks to ensure the data is accurate.
Discussion questions:
What does Kevin mean when he uses the word ‘standard’?
What are two ways the data is checked?
Why is it important for climate data to be both robust and transparent?
This gathering, analysing and interpreting of data is vital to understanding climate change and informing strategies to slow or mitigate its effects.
Taking on the challenge – Ministry for the Environment and Stats NZ
The New Zealand Ministry for the Environment states that climate change is the biggest environmental challenge of our time. The seriousness of this challenge is reflected by the efforts that government agencies, universities and others are investing in climate change research.
The Ministry for the Environment provides information about the status of the environment. It works with Stats NZ, New Zealand’s official data agency, to provide environmental reports – including Our atmosphere and climate 2020. The report outlines what is happening to our climate, why it is happening and how climate change is affecting the things we care about.
Information used in the environmental reports produced by the Ministry for the Environment and Stats NZ comes from many sources, including data collected and analysed by scientists in central government, regional councils and the following organisations.
Journey of the greenhouse gas data
NIWA scientist Gregor Macara tells us about collecting air samples and the data that comes from them, which is then checked by experts like Drew Bingham from the Ministry for the Environment.
Question for discussion:
Why do you think scientists collect manual samples in flasks?
How do you think scientists make sure measurements are robust over time?
Research institutes and centres
Several Crown research institutes have climate change research as part of their core business. For example, the National Institute of Water and Atmospheric Research (NIWA) monitors the atmosphere, climate and the oceans. Manaaki Whenua – Landcare Research monitors land-based ecosystems and land use. AgResearch works to understand and mitigate the effects of greenhouse gas emissions from primary industries – alongside the New Zealand Agricultural Greenhouse Gas Research Centre and the Pastoral Greenhouse Gas Research Consortium.
The New Zealand Climate Chang e Research Institute at Victoria University of Wellington engages in research to inform policy and contribute to public debates about climate change. Other universities in Aotearoa also conduct similar research.
National Science Challenges
The National Science Challenges are tackling the country’s biggest science-based challenges. The Deep South Challenge is most closely linked to climate change. Its aim is to understand the role of the Antarctic and Southern Ocean in determining our future climate and the potential impacts for our economy and natural resources. New Zealand’s Biological Heritage Challenge works to mitigate the effects of climate change and prevent biodiversity loss. One of the objectives of the Resilience to Nature’s Challenges Challenge is to investigate hazards associated with sea level rise and climate change.
How do we know the interpretation of the data is accurate?
Objectivity and careful scientific processes are key when collecting climate change evidence. Climate experts James Renwick and Drew Bingham explain why.
Using data to make informed decisions
Climate science is incredibly complex. Experts from these organisations (and others) have been able to gather enormous amounts of data through direct observation such as decades of monitoring via weather stations and satellites. They’ve been able to observe past climates via natural timelines like ice cores and sediment cores. Climate models have helped them learn about the interactions between Earth’s land, water and atmospheric systems. Each of these pieces of evidence comes together to explain how humans contribute to climate change.
Activity ideas
Delve into data – these activities use visual representations and datasets from Our atmosphere and climate 2020:
Related content
Find out how the primary sector is collaborating to reduce climate change.
Useful links
Find out how various agencies are taking up the challenge of climate change research.
The Ministry for the Environment and Stats NZ produce New Zealand’s Greenhouse Gas Inventory – an annual report of all human-induced emissions and removals of greenhouse in Aotearoa. The inventory is one of the most important publicly available statistics for understanding how well New Zealand is performing.
Acknowledgement
This resource has been produced with the support of the Ministry for the Environment and Stats NZ. (c) Crown Copyright.
Our atmosphere and climate 2020
The Ministry for the Environment and Stats NZ produce New Zealand’s Environmental Reporting Series. Our atmosphere and climate 2020 focuses on climate change, with an overview of what is happening to our climate and how this affects many of the things we care about.
