Measuring the changing climate

The Challenge

Climate science is a global pursuit that demands high levels of measurement accuracy and consistency across vast geographic scales and over many decades.

Aotearoa’s contribution to climate research is led by Earth Sciences New Zealand (ESNZ)^[1], an organisation formed in 2025 through the merger of NIWA (National Institute of Water and Atmospheric Research) and GNS Science, with MetService joining in 2026. This brings together bringing all of New Zealand’s natural hazard monitoring into one organisation. ESNZ collects climate data from instruments in a diverse set of environments – everything from alpine glaciers to deep ocean moorings – all with the goal of better understanding our land, air, and water.

A priority for all climate scientists is ensuring that each measured quantity – whether temperature, humidity, greenhouse gas concentration, or UV levels – can be reliably compared locally and internationally. Rigorous traceability of these measurements to the International System of Units (SI) and other international standards is the best way to provide that unbroken chain of trust.

The challenge extends beyond individual measurements. Climate and weather models integrate data from multiple sources: satellite observations, ground-based weather stations, ocean buoys, and atmospheric sensors, as well as historical records. The accuracy of these measurements directly affects the reliability of the models in which they are used and, consequently, our ability to predict future climate and weather trends and impacts. Inaccurate, inconsistent, or incomplete data can lead to flawed models. And flawed models, in turn, can skew policymaking decisions, and undermine public trust in the science of climate change.

The Solution

As members of New Zealand’s national metrology institute, we here at MSL provide the metrology foundations that underpin NZ’s measurements for climate science.

MSL maintains the primary standards for pressure, humidity, temperature, and light, and offers calibration services that ensure climate-monitoring instruments meet international specifications. For instance, MSL’s temperature and humidity standards have enabled ESNZ to calibrate reference thermometers used across New Zealand’s climate network, ensuring measurements from Kaitaia to Invercargill are directly comparable and are consistent with international measurements. MSL has also calibrated ESNZ’s UV sensors, which monitor long-term trends in ultraviolet radiation, and the barometers that help to establish our weather forecasts.

By participating in international comparisons coordinated through the BIPM (Bureau International des Poids et Mesures), MSL ensures New Zealand’s measurements align with the global measurement system. Furthermore, MSL scientists participate in international efforts to improve the definitions of, and measurement practices for, emerging climate variables such as ocean salinity, seawater pH, and atmospheric relative humidity.^[2]

The Impact

ESNZ’s seven-station temperature series – one of the Southern Hemisphere’s longest continuous climate records – derives credibility from metrologically-sound calibration practices. When ESNZ tracks glacier retreat or issues climate outlooks, the underlying measurements carry traceable uncertainty evaluations that strengthen scientific confidence in those measurements.

For a country where climate impacts – from coastal erosion to agricultural shifts – demand accurate local projections, the precision enabled by metrology translates directly into better-informed decision-making within New Zealand.

Internationally, robust metrology enables our climate data to contribute meaningfully to global assessments led by the Intergovernmental Panel on Climate Change. This supports evidence-based policy decisions on emissions reductions and climate adaptation, and is crucial for tracking progress against climate goals.

Ultimately, metrology transforms climate science from observation into quantified knowledge, providing the trust and certainty essential for understanding our changing planet.

“Accurate measurements of the weather are vital, not only for research into how our climate is changing over long time periods, but they are also the most critical input for all numerical weather prediction models that form the basis or our daily weather forecasts and warnings. The Observations team at MetService – who service and calibrate a large network of weather stations around NZ – have worked with MSL for decades to ensure weather data from NZ is of the highest standard, for use here and around the world."

- Chris Noble, Chief Meteorologist, MetService