Generated Summary
This document presents data on the trends of atmospheric nitrous oxide (N2O) measured by the Global Monitoring Division (GMD) of NOAA’s Earth System Research Laboratory. The study focuses on globally-averaged, monthly mean N2O abundance determined from marine surface sites. The research involves analyzing time-series data starting in 2001 to assess the annual increase in atmospheric N2O. The methodology includes smoothing data for each site, fitting smoothed values as a function of latitude, and calculating global means from the latitude fits. The document provides monthly and annual mean data, including the annual increase in N2O from January 1 to January 1 of the following year, after removing the seasonal cycle. The initial estimates for the annual increase are reported in April of the following year and are subject to change as more data becomes available. The data is updated monthly as new samples are processed and added to the analysis, improving the accuracy of the initial estimates by increasing data density and reducing “end effects” of the curve fitting procedures. The document also acknowledges the potential for bias in initial estimates and describes the methods used to estimate the uncertainty in the global annual N2O increase.
Key Findings & Statistics
- February 2021: 334.0 ppb
- February 2020: 332.6 ppb
- The document presents graphs showing globally-averaged, monthly mean atmospheric nitrous oxide abundance determined from marine surface sites.
- The graphs include the monthly means for the last four years plus the current year and the NOAA time-series starting in 2001.
- Annual Increase in Globally-Averaged Atmospheric Nitrous Oxide:
- 2001: 0.71 ± 0.12
- 2002: 0.50 ± 0.15
- 2003: 0.80 ± 0.15
- 2004: 0.53 ± 0.16
- 2005: 0.86 ± 0.15
- 2006: 0.69 ± 0.12
- 2007: 0.91 ± 0.14
- 2008: 0.91 ± 0.14
- 2009: 0.76 ± 0.16
- 2010: 1.08 ± 0.15
- 2011: 0.91 ± 0.14
- 2012: 0.81 ± 0.13
- 2013: 1.01 ± 0.15
- 2014: 1.24 ± 0.15
- 2015: 0.90 ± 0.14
- 2016: 0.67 ± 0.16
- 2017: 1.01 ± 0.15
- 2018: 1.16 ± 0.14
- 2019: 0.92 ± 0.13
- 2020: 1.31 ± 0.13
- The document explains that the annual increase in atmospheric N2O is the increase in its abundance from January 1 in one year to January 1 of the next year, after the seasonal cycle has been removed.
- The annual increase represents the sum of all N2O added to and removed from the atmosphere during the year, from both human activities and natural processes.
- The initial estimate for the annual increase is reported in April of the following year.
- The study indicates that initial estimates of the N2O annual increase made for the previous year are biased compared to those that follow using additional data, with an average bias in the initial estimate of +0.12 ± 0.08 ppb yr-1.
- The document notes that this bias slowly decreases over the next few months, with bias values potentially varying significantly in any given year (up to ±0.25 ppb yr-1).
- The initial value for monthly mean N2O is typically too large, by up to 0.4 ppb.
- The estimated uncertainty in the global annual N2O increase varies by year and is estimated using two terms: a “bootstrap” (resampling) method and a Monte Carlo method.
Other Important Findings
- The document states that the data is collected from a globally distributed network of air sampling sites.
- The red lines and circles in the figures represent globally averaged monthly mean values centered on the middle of each month.
- The black line and squares show the long-term trend where the average seasonal cycle has been removed.
- The initial, April estimate of the annual increase is likely to change significantly as more data are added to the analysis.
- The document mentions the impact of adding new data to the parameters reported here and summarizes the results.
- The behavior of initial annually-averaged means and monthly-averaged means are similar.
Limitations Noted in the Document
- Values for the last year are preliminary pending recalibrations of standard gases and other quality control steps.
- The initial, April estimate of the annual increase is likely to change significantly as more data are added to the analysis.
- Initial estimates of the N2O annual increase made for the previous year are biased compared to those that follow using additional data.
- The average bias in the initial estimate is +0.12±0.08 ppb yr-1.
- Bias in the annual increase can be much larger than the average, with bias up to ±0.25 ppb yr-1.
- For monthly mean N₂O, the initial value is typically too large, by up to 0.4 ppb.
Conclusion
The document provides an overview of the trends in atmospheric nitrous oxide (N2O) as measured by NOAA’s Global Monitoring Laboratory. The research emphasizes the importance of ongoing monitoring and the continuous refinement of data through the addition of new samples. The data shows monthly and annual means of N2O, with specific values for recent years, and the annual increase based on globally averaged marine surface data. A key finding is that initial estimates of the annual increase are subject to change as more data becomes available, highlighting the need for a dynamic approach to understanding atmospheric N2O levels. The study emphasizes that initial estimates of the N2O annual increase made for the previous year are biased compared to those that follow using additional data. The document also highlights the methodology used to create the global averages, including smoothing and fitting techniques, and describes how uncertainty is estimated using a bootstrap method and a Monte Carlo method. The findings are based on a globally distributed network of air sampling sites, indicating a comprehensive approach to understanding global N2O trends. The ongoing collection and analysis of data are crucial for refining our understanding of atmospheric N2O levels and their changes over time, which helps us gain further insight into the anthropogenic impacts and natural processes that drive these changes. The document provides crucial information about the accuracy of the preliminary data and how these are prone to change as more samples and data are included in the analysis. The document also highlights how the data and its analysis is an ongoing process and that further changes are likely to occur in the future.