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.

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.

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.

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.

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 Change 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.

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.