Climate

Our research covers the spectrum from experimental studies of processes, to monitoring and modelling. Central research topics include long-lived greenhouse gases, short-lived climate forcing agents and the climate system itself.

Greenhouse gases

NILU measures greenhouse gases and other relevant factors at the Zeppelin Observatory in Svalbard. From the time when this monitoring started, the CO2 concentration has risen every year, in line with the increase in man-made emissions.

Many of the gases are measured as part of the Norwegian Environment Agency’s national monitoring programme. Results and interpretations of trends are reported annually.

Descriptions of these measurement programmes for long-lived greenhouse gases are available on the webpages on our various observatories. Most data are available from our database EBAS.

Key activities aimed at increasing our understanding of long-lived greenhouse gases:

• Describing and understanding changes in regional, hemispheric and global levels of greenhouse gases
• Understanding the atmospheric budget of the various greenhouse gases
• Quantifying changes in emissions by use of observational methods
• Understanding the processes that affect natural emissions and exchanges between atmosphere, land and sea
• Developing tools to examine whether mitigation measures work as intended
• Developing methods and instruments that will give more precise measurements of atmospheric components old and new
• Contributing to the development of infrastructure adapted to future needs for observation networks, interpretation and analysis

Short-lived climate forcers

The most important way of reducing global warming is to substantially reduce CO2 emissions, but this will not happen soon enough to prevent rapid melting of ice in the Arctic. Thus, we must also reduce atmospheric levels of short-lived climate forcers such as methane, tropospheric ozone and aerosols.

NILU measures methane, ozone and aerosols at several of our observatories.

The climate system and meteorology

Geophysics describes the physics of the Earth and the physical processes that affect it. This includes aspects of the Earth’s interior, oceanography, meteorology, atmospheric physics and hydrology.

NILU studies a range of geophysical processes with impact on climate, from research on soil (soil moisture and snow), via atmospheric water transport and circulation, to studies of the optical properties of clouds.

Atmospheric circulation and “teleconnections”

Global atmospheric circulation patterns are highly complex. Climatic variability in one region can be closely linked to climate variations in areas several hundred miles away. Such phenomena are often called “teleconnections”.

At NILU, we do research on large-scale circulation patterns and their impact on various climate parameters – from sea ice to stratospheric ozone.

The Arctic and the High North are key areas for studying the changing climate. Observations during the last decade indicate that the sea ice is melting much faster than most climate models predict. This melting might be related to increased cyclone activities in the High North during summer.

A key task at NILU is to identify and distinguish climate variability caused by natural phenomena versus anthropogenic influences. The climate variability we observe will always be affected by both factors.

Atmospheric water transport

Atmospheric water transport from remote areas often contributes to episodes of extreme precipitation over Norway. This can happen when mid-latitude cyclones induce atmospheric “rivers”.

Research on the physical properties, structure and strength of this water transport is a focus area for NILU.

This work is important for understanding the impact of sea surface temperature (SST) on extreme precipitation and the climatological origin of precipitation in Norway and the High North. It will provide useful knowledge about the connection between climate change and extreme weather events.

Land data (temperature, snow, assimilation; LDAS)

Soil moisture, snow and soil temperature are geophysical parameters that have a substantial impact on vegetation and climate. These parameters are important for plant transpiration and photosynthesis, and will have a significant impact on the Earth’s hydrological cycle.

Variations and trends in soil moisture reflect changes in precipitation and radiation, and contribute to climate feedback mechanisms on a local, regional and global scale.

Researchers at NILU have developed the land data assimilation system (LDAS), in cooperation with the Norwegian Meteorological Institute (met.no) and Meteo France. The system is based on different variants of the Ensemble Kalman Filter (EnKF) and Extended Kalman Filter (EKF), and is linked to the offline SURFEX land data model. Soil moisture data from AMSR-E, ASCAT and SMOS are used in the assimilation.

The system can provide important information about soil moisture, snow and surface temperatures in Scandinavia and Europe. We aim to integrate LDAS into meteorological weather prediction models to improve weather forecasts.

Clouds and radiation

Clouds have a major impact on climate. They reflect solar radiation back into space, and consequently cool the Earth’s surface. Conversely, by absorbing infrared radiation (IR) from the Earth and re-emitting some of this radiation back to the surface, clouds can enhance the greenhouse effect.

The relationship between these two phenomena, i.e. the cooling effect from reflection of solar radiation and the warming effect from absorption of IR, determines whether a certain type of cloud will have a net cooling or warming effect.

NILU employs some of the world-leading experts on radiation transport, and has been a key player in the development of the LIBRADTRAN model.