From acda5321151096c768ca62e7cc946ebbd2de7d38 Mon Sep 17 00:00:00 2001
From: Daniel Huppmann <dh@dergelbesalon.at>
Date: Mon, 20 Jul 2026 09:51:33 +0200
Subject: [PATCH 1/3] Add an IamDataFrame.series attribute to get internal
 `_data`

---
 pyam/core.py       | 5 +++++
 tests/test_core.py | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/pyam/core.py b/pyam/core.py
index b65714104..7ba2ad36f 100755
--- a/pyam/core.py
+++ b/pyam/core.py
@@ -433,6 +433,11 @@ def data(self):
             return pd.DataFrame([], columns=self.dimensions + ["value"])
         return self._data.reset_index()
 
+    @property
+    def series(self):
+        """Return the timeseries data as an indexed :class:`pandas.Series`"""
+        return self._data
+
     def sort_data(self, inplace=False):
         """Sort timeseries data by index and coordinates
 
diff --git a/tests/test_core.py b/tests/test_core.py
index 9dbf80f5f..372c0583e 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -332,6 +332,14 @@ def test_print_empty(test_df_year):
     assert obs == exp
 
 
+def test_pandas_types(test_df):
+
+    series = test_df.series
+    data = test_df.data
+
+    pdt.assert_frame_equal(series.reset_index(), data)
+
+
 def test_as_pandas(test_df):
     # test that `as_pandas()` returns the right columns
     df = test_df.copy()

From d51237b6c81f612d1b87f139052e6973141a0270 Mon Sep 17 00:00:00 2001
From: Daniel Huppmann <dh@dergelbesalon.at>
Date: Mon, 20 Jul 2026 10:04:57 +0200
Subject: [PATCH 2/3] Add to release notes

---
 RELEASE_NOTES.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index fc8aba068..764d06d3a 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,3 +1,8 @@
+# Next release
+
+- [#989](https://github.com/IAMconsortium/pyam/pull/989) Add an `IamDataFrame.series` attribute to get timeseries data
+  as **pd.Series**
+
 # Release v3.3.3
 
 ## Highlights

From 7c0f55cfbf6b266383e96add24bf1f074597e2c9 Mon Sep 17 00:00:00 2001
From: Daniel Huppmann <dh@dergelbesalon.at>
Date: Wed, 22 Jul 2026 18:56:41 +0200
Subject: [PATCH 3/3] Yield a copy of the pd.Series

---
 pyam/core.py       | 2 +-
 tests/test_core.py | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/pyam/core.py b/pyam/core.py
index 7ba2ad36f..4c11b8132 100755
--- a/pyam/core.py
+++ b/pyam/core.py
@@ -436,7 +436,7 @@ def data(self):
     @property
     def series(self):
         """Return the timeseries data as an indexed :class:`pandas.Series`"""
-        return self._data
+        return self._data.copy()
 
     def sort_data(self, inplace=False):
         """Sort timeseries data by index and coordinates
diff --git a/tests/test_core.py b/tests/test_core.py
index 372c0583e..8c7aa6796 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -337,8 +337,13 @@ def test_pandas_types(test_df):
     series = test_df.series
     data = test_df.data
 
+    # assert that data and series yield the same result as different types
     pdt.assert_frame_equal(series.reset_index(), data)
 
+    # check that `series` yields a copy and changes to not affect the IamDataFrame
+    series.iloc[0] = -2
+    pdt.assert_frame_equal(test_df.series.reset_index(), data)
+
 
 def test_as_pandas(test_df):
     # test that `as_pandas()` returns the right columns