Global Mean Sea Level Rise Trend is 3.35 mm/year

Here is the very latest measurement of Global Mean Sea Level (GMSL).  The trend is 3.35 mm/yr over the period 1993-2017. Which confirms we are on track for 40cm of sea level rise by 2050-2060 as predicted.

multiple trends

And Yes – the rate of sea level rise is accelerating

More importantly, the GMSL curve over that period shows a net acceleration, estimated at 0.08 mm/yr. 

NASA has this video on the accelerating trend 

This data comes from the WCRP Global Sea Level Budget Group a massive international effort involving scores of scientists from 60 research teams in the sea level scientific community worldwide. The focus of the study is on observations from a combination of a broad range of space-based and in situ observations such as tidal gauges, and considers the high-precision altimetry (satellite) era starting in 1993. See also 

Our local resident climate change denier has suggested that one particular study from NOAA has doctored its results. But there are six different altimetry-based time series.   They are – AVISO/CNES, SL_cci/ESA, University of Colorado, CSIRO, NASA/GSFC, and NOAA. These missions combine to provide the most accurate long-term stability at global and regional scales.

These figures are a Global Mean, but the 2017 MfE Guidance on Coastal Hazards points out that there are regional variations in the rates of sea level rise. In New Zealand waters the rate of sea level rise has been significantly higher than the global mean.

“Based on comparative analysis of satellite altimeter measurements from 1993 to 2015 inclusive, the trend for the absolute sea-level rise in the wider New Zealand exclusive economic zone ocean waters has been 4.4±0.9 mm/yr”

global sea level trends since 2006

Our local village idiot denier would have you believe you should use the average sea level rate over the last 100 years and then just project that same low rate into the future!  This simple graph clearly shows the acceleration of the rate from 0.6mm/yr 1900-1930, 1.4mm/yr 1930-1992, 2.6mm/yr 1993-2015, and now 3.3mm/yr 1993-2018Screen Shot 2018-05-21 at 5.09.56 PM

What these figures confirm is that we are definitely on track for a sea-level rise of 40 cm by 2060. For high-risk places like Thames even 40 cm could be catastrophic and has the potential to make much of the foreshore and parts of the CBD unlivable.

Which is why we urgently need expert mapping and risk assessment for Thames and other high-risk areas. Hopefully, the $2.6 million set aside by TCDC will be used for an urgent work programme on these issues so that we can then concentrate on solutions.