Earth is heating up due to rapidly increasing concentrations of greenhouse gases in the atmosphere. Significant changes to the climate are occurring as a result, which are affecting our natural environment, primary sector, infrastructure and built environment, as well as human health.
Impacts of a warming climate
- Earth's average temperature has increased by about 1 degree C since humans started using fossil fuels. Most of the warming has occurred since the mid-1980s, with 18 of the 19 warmest years on record occurring since 2000.
- The polar ice caps have melted faster in the last 20 years than at any other time in the last 10,000 years, and the majority of glaciers around the world are retreating.
- The sea level has risen by about 20cm since scientific records began in 1880, and the rate of rise has increased in recent decades.
- There has been a 30% increase in ocean acidity in the last 250 years.
- Higher temperatures have resulted in more heat waves, warmer winters, and heavier rainfall.
In New Zealand:
- Temperatures are about 1 degree C warmer than they were a century ago, with three of the hottest years on record occurring since 2014.
- Sea levels have risen 14-22cm since the early 1900s.
- Our glaciers have lost 25% of their ice in the past 40 years.
- The country is experiencing fewer frost days and more warm days. Some locations are also experiencing drier soils and altered precipitation patterns.
- More intense weather events (droughts and storms) have occurred in many parts of the country in the last few years, and at unexpected times of the year.
These impacts are set to continue.
Climate change projections
As our climate changes, it might not be possible to farm in the same way or the same places as we can now.
A couple of degrees of warming might not seem much, but it can have a big effect on crop and pasture growth, and on pests and diseases.
Here are some projections:
- Many places will see more than 80 days per year above 25 degrees C by 2100, which will have a significant impact on ryegrass growth (which prefers temperatures in the range of 5-18 degrees C) and animal performance.
- Annual average rainfall is expected to decrease in the northeastern South Island and northern and eastern North Island and increase in other parts of New Zealand.
- Farmers in dry areas can expect up to 10% more drought days by 2040.
There are also implications for freshwater:
- Increased runoff will occur in the south and west of the South Island.
- Reduced runoff will occur in the northeast of the South Island and in the east and north of the North Island
- Annual flows will increase 5-10% in eastward rivers with headwaters in the Southern Alps (in winter/spring).