IPCC: Global warming continues
Over the past 130 years, the global average temperature has increased by 0.9 °C. Since the beginning of the 20th century, sea levels have risen by 20 centimetres. In its latest report, the Intergovernmental Panel on Climate Change (IPCC) is even more confident than before about the human influence on our global climate.
The warming of the earth does not follow a straight line, but is subject to fluctuations. After having accelerated during the last 30 years of the previous century, warming has been slower over the past 15 years. Depending on the amount of greenhouse gases in the atmosphere, the global average temperature will continue to rise by 0.3 to 4.8 °C, up to the end of the 21st century, compared to late 20th century levels. These conclusions by the United Nations Intergovernmental Panel on Climate Change (IPCC) confirm the anthropogenic influence of greenhouse gas emissions on our climate. This information can be found in the first part of the fifth Assessment Report of the IPCC, which was formally accepted by climate scientists and policymakers in Stockholm on 26 September of this year.
Warming continues
Between 1880 and 2012, the global average temperature has gone up by 0.85 °C. There is hardly any doubt that climate change of the past 60 years was caused by anthropogenic greenhouse gas emissions. The last 30 years very likely constituted the warmest period of the past 1400 years. During the last 15 years, the rate of temperature rise has decreased. This is caused by the natural variability in the climate system, less solar radiation, and dust particles emitted by volcanoes and industry. Global warming will continue during this century. The IPCC estimates that by 2025 the global average temperature will be 0.3 to 0.7 °C higher than it was at the end of the 20th century. Depending on greenhouse gas concentrations in the atmosphere, global warming could reach 0.3 to 4.8 °C by the end of this century.
New sea level rise projections
The IPCC has adjusted its sea level rise projections upward, due to a strong improvement in the understanding of ice sheets. Current sea level rise can be explained by the thermal expansion of sea water, melting glaciers, collapsing ice sheets, and changes in groundwater storage, irrigation practices, and dams. Over the 1901–2010 period, sea level rise was 19 centimetres. This century, a further rise of between 26 and 82 centimetres could be seen.
Transparent report
An international team of scientists, including those from the Royal Netherlands Meteorological Institute (KNMI), have worked on the fifth report of the IPCC. After criticism of the last report, from 2007, the IPCC modified its procedures and increased the transparency of its work. The comments of hundreds of independent scientists, also from the Netherlands, were processed for the final version of the report. Both the comments and the response by IPCC authors will become publicly available soon.
New measurement data covering longer periods of time, new models and more computing power have increased the understanding of the climate system. The new data confirm many of the conclusions in previous IPCC reports.
Implications for the Netherlands
Observations have shown that temperatures in the Netherlands have clearly risen faster than the global average. Future temperature projections for the Netherlands are also higher than global projections. Precipitation also is likely to increase, while projections of sea level rise for the Netherlands are close to the global average. The KNMI is expected to publish new regional climate scenarios in the spring of 2014, translating the IPCC findings into the Dutch situation, in more detail.